In cooperation with the Coeur d’Alene Tribe

Baseline, Historic and Background Rates of 

Deposition of Lead-Rich Sediments on the 

Floodplain of the Coeur d’Alene River, Idaho 

By Arthur A. Bookstrom1, Stephen E. Box1, Robert S. Fouseck2, 

John C. Wallis1, Helen Z. Kayser1 and Berne L. Jackson3 

2004, revised 2013

1 USGS, 904 West Riverside Avenue, Room 202, Spokane, WA 99201

2 PO Box 2756, Auburn, AL 36831

3 Coeur d’Alene Tribe, Plummer, ID 83851

Any use of trade, firm, or product names is for descriptive purposes only and does not 

imply endorsement by the U.S. Government

Open-File Report 2004-1211, Version 1.1

U.S. Department of the Interior

U.S. Geological Survey
2 

U.S. Department of the Interior 

Gale A. Norton, Secretary 

U.S. Geological Survey 

Charles G. Groat, Director 

U.S. Geological Survey, Reston, Virginia 2006

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Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report. 
3 

Contents 

Contents .......................................................................................................................................................................................... 3 

Abstract ........................................................................................................................................................................................... 7 

Introduction..................................................................................................................................................................................... 7 

Purpose....................................................................................................................................................................................... 8 

Overview .................................................................................................................................................................................... 8 

Description of Study Area and Surroundings.................................................................................................................................. 8 

Water Levels and Topography ................................................................................................................................................... 9 

Precipitation and Vegetation ...................................................................................................................................................... 9 

Deforestation, Runoff and Floods ............................................................................................................................................ 10 

Upper Perennial Riverine Subsystem....................................................................................................................................... 10 

Lower Perennial Riverine Subsystem....................................................................................................................................... 10 

Coeur d’Alene Mining Region ................................................................................................................................................. 11 

History of Production of Ore, Lead, Zinc, and Silver.......................................................................................................... 11 

History of Tailings Production ............................................................................................................................................ 12 

History of Tailings-Management Practices ......................................................................................................................... 12 

Data Sets and Methods.................................................................................................................................................................. 13 

Sampling Strategies.................................................................................................................................................................. 13 

Sampling Methods.................................................................................................................................................................... 14 

Chemical Analytical Methods .................................................................................................................................................. 14 

Data-Classification and Estimation Methods ........................................................................................................................... 14 

Descriptive Summary Statistics .................................................................................................................................................... 15 

Statistical Definitions ............................................................................................................................................................... 15 

Statistical Characterizations ..................................................................................................................................................... 15 

Statistically Based Estimates.................................................................................................................................................... 16 

Stratigraphy of Unconsolidated Sediments ................................................................................................................................... 16 

Pre-Industrial Sediments .......................................................................................................................................................... 16 

Background Sediment-Deposition Rates (sdrBG) ............................................................................................................... 16 

Background Lead Concentrations (PbBG) .......................................................................................................................... 17 

The Section of Lead-Rich Sediments (PbR)............................................................................................................................. 17 

Time-Stratigraphic Markers ..................................................................................................................................................... 17 

Surface at the Time of Sampling (1991 to 1998)................................................................................................................. 18 

Mt. St. Helens Volcanic-Ash Layer (1980) ......................................................................................................................... 18 

Base of Section of Lead-Rich Sediments (~1903)............................................................................................................... 18 

Time-Stratigraphic Intervals..................................................................................................................................................... 19 

Pre-Remedial Baseline Interval, AA (1980 ~1993)............................................................................................................. 19 

Historic Floodplain-Contamination Interval, BA, (~1903 to 1980)..................................................................................... 19 

Early Post-Tailings-Release Subinterval, BA1 (~1968 to 1980)..................................................................................... 19 

Tailings-Release Subinterval, BA2 (~1903 to ~1968)..................................................................................................... 20 

Jig Tailings-Release Sub-Subinterval, BA2J (~1903 to ~ 1918)..................................................................................... 20 

Flotation Tailings-Release Sub-Subinterval, BA2F (~1918 to ~ 1968).......................................................................... 20 

Early Metal-Enrichment Interval, EME (~1893 ~1903)................................................................................................. 20 

Character of Sediments by Depositional Setting........................................................................................................................... 20 

Riverbed Sediments.................................................................................................................................................................. 21 

Riverbank and Levee Sediments .............................................................................................................................................. 21 

Palustrine Sediments ................................................................................................................................................................ 21 

Lacustrine Sediments ............................................................................................................................................................... 22 

Baseline Depositional Rates and Lead Concentrations ................................................................................................................. 22 

Baseline Sediment-Deposition Rates, Overall Summary Statistics.......................................................................................... 22 

Baseline Lead Concentration, Overall Summary Statistics ...................................................................................................... 23 

Baseline Sediments of Various Depositional Settings and Areas............................................................................................. 23 

Riparian Riverbanks, Baseline Sediments, Main Stem of Coeur d’Alene River................................................................. 24 

Comparison to Baseline Sediments on Banks of nearby Rivers...................................................................................... 24 

Riparian Levee Uplands, Baseline Sediments ..................................................................................................................... 24 

Riparian Distributary Levees and Sand Splays, Baseline Sediments................................................................................... 24 

Wetlands, Palustrine and Littoral Baseline and Surface Sediments..................................................................................... 25 

Lane Marsh South, Palustrine Baseline and Surface Sediments..................................................................................... 25 
4 

Medicine Lake, Littoral Baseline and Surface Sediments............................................................................................... 25 

Cave Lake, Littoral Baseline and Surface Sediments ..................................................................................................... 25 

Bare Marsh, Palustrine Baseline and Surface Sediments............................................................................................... 26 

Thompson Lake, Littoral Baseline and Surface Sediments............................................................................................. 26 

Thompson Marsh, Littoral Baseline and Surface Sediments .......................................................................................... 26 

Anderson Lake, Littoral Baseline and Surface Sediments .............................................................................................. 26 

Limnetic Post-Tailings-Release Sediments ......................................................................................................................... 26 

Medicine-Lake, Limnetic Post-Tailings-Release Sediments ........................................................................................... 27 

Killarney Lake, Limnetic Post-Tailings-Release Sediments............................................................................................ 27 

Thompson Lake, Limnetic Post-Tailings-Release Sediments.......................................................................................... 28 

Depositional Rates and Lead Concentrations through Time......................................................................................................... 28 

Historic and Baseline Depositional Rates................................................................................................................................. 28 

Historic and Baseline Lead Concentrations.............................................................................................................................. 29 

Early Post-Tailings-Release Depositional Rates (sdrBA1) ...................................................................................................... 30 

Tailings-Release Depositional Rates (sdrBA2)........................................................................................................................ 30 

Lead in Baseline versus Early Post-Tailings-Release Sediments............................................................................................. 31 

Lead in Tailings-Release Sediments (PbBA2) ......................................................................................................................... 31 

Lead in Sediments Deposited through Time ................................................................................................................................. 31 

Tonnage-Accumulation Rates for Sediments and Lead ........................................................................................................... 32 

Total Tonnage of Lead in Floodplain Sediments ..................................................................................................................... 32 

Sources and Transport of Lead-Rich Sediments ........................................................................................................................... 33 

Secondary Sources of Lead-Rich Sediments Deposited on the Floodplain.............................................................................. 33 

Transport and Deposition of Lead-Rich Sediment ................................................................................................................... 33 

Physical Transport of Lead-Bearing Particles ..................................................................................................................... 34 

Transporting, Dispersing, and Depositing Subsystems ....................................................................................................... 35 

Seasonal Cycle of Discharge and Sediment Transport ........................................................................................................ 35 

Active versus Stored Riverbed Sediment ................................................................................................................................. 36 

Down-Cutting versus Aggradation in the River Channel .................................................................................................... 36 

Deposition and Storage of Lead-Rich Sediment on the Floodplain..................................................................................... 37 

Fluvial Process Rates................................................................................................................................................................ 37 

Annual Rates of Riverbank Erosion .................................................................................................................................... 37 

Annual Rates of Deposition from Riverbank to Levee Crest .............................................................................................. 38 

Annual Rates of Sediment Transport in the Coeur d’Alene River....................................................................................... 38 

Annual Rates of Deposition of Floodplain Sediments and Coeur d’Alene Lake Sediments ............................................... 39 

Mobilization and Transport of Sediment along the Main Stem........................................................................................... 39 

Mobilization of Sediment from Main-Stem Riverbanks................................................................................................... 39 

Mobilization and Transport of Sediment from the Main-Stem Riverbed ........................................................................ 40 

River Transport versus Floodplain Deposition Rates .......................................................................................................... 40 

Long-Term Contamination in River Systems........................................................................................................................... 40 

Modeling Studies................................................................................................................................................................. 40 

Stratigraphic Studies............................................................................................................................................................ 41 

Long-Term Future Contamination in the Coeur d’Alene River Valley............................................................................... 41 

Long-Term Monitoring........................................................................................................................................................ 41 

Implications for Remediation........................................................................................................................................................ 41 

Remediation Options for Reducing Metal contents of Flood-Borne Sediment ........................................................................ 43 

Source Control by Removal or Stabilization of Riverbanks................................................................................................ 43 

Source Control by Periodic Removal of Sand Splays.......................................................................................................... 43 

Local Dilution of Suspended Sediment with Low-Metal Sediment .................................................................................... 44 

Riverbed Dredging as Source Control................................................................................................................................. 44 

Riverbed Source Control by In-Situ Stabilization ............................................................................................................... 45 

Conclusions................................................................................................................................................................................... 45 

Acknowledgements....................................................................................................................................................................... 46 

Literature Cited ............................................................................................................................................................................. 46 

Appendix 1. Data Table ................................................................................................................................................................ 48 

Appendix 2. Metadata ................................................................................................................................................................... 49 

 

Illustrations 

Plate 1. Map of surficial geology, Coeur d’Alene River valley, Idaho, showing baseline sediment-deposition rates. 
5 

Plate 2. Map of surficial geology, Coeur d’Alene River valley, Idaho, showing baseline lead concentrations 

Figure 1. Location map showing the Coeur d'Alene River system, CdA Lake, and the Spokane River......................................... 8 

Figure 2. Index and location maps showing the Coeur d’Alene mining region, upstream from the main stem of the Coeur 

d’Alene River and Coeur d’Alene Lake. ............................................................................................................................... 8 

Figure 3. Map showing the upper (eastern) part, main stem of the Coeur d’Alene River valley. ................................................. 10 

Figure 4. Map showing the middle part, main stem of the Coeur d’Alene River valley............................................................... 10 

Figure 5. Map showing the lower (western) part, main stem of the Coeur d’Alene River valley................................................. 10 

Figure 6. Block diagram showing features typical of the floodplain of the lower perennial subsystem of the Coeur d’Alene 

River system, west of Cataldo Landing. .............................................................................................................................. 10 

Figure 7. Graphs showing annual production of ore, lead and zinc, and a) production-related events, b) tailings-related events.12 

Figure 8. Lead concentration profiles for stratigraphic sections of sediments in the Coeur d’Alene River and on its floodplain.20 

Figure 9. Cumulative frequency diagram showing baseline sediment-deposition rates (sdrAA) for sediments deposited on the 

floodplain from 1980 to about 1993. ................................................................................................................................... 23 

Figure 10. Scatter diagram showing baseline sediment-deposition rates (sdrAA) versus distance (m) from the Coeur d’Alene 

River. ................................................................................................................................................................................... 23 

Figure 11. Frequency diagram of baseline sediment-deposition rates (sdrAA). ........................................................................... 23 

Figure 12. Frequency diagram of natural logs of baseline sediment-deposition rates (ln sdrAA). ............................................... 23 

Figure 13. Cumulative frequency distribution of baseline lead concentrations (PbAA) in floodplain sediments......................... 23 

Figure 14. Scatter diagram showing ppm Pb in floodplain sediments of the baseline interval (PbAA) versus distance from the 

Coeur d’Alene River............................................................................................................................................................ 23 

Figure 15. Frequency diagram of baseline lead concentrations (PbAA) in floodplain sediments................................................. 23 

Figure 16. Frequency diagram of natural logs of baseline lead concentrations (PbAA) in floodplain sediments......................... 23 

Figure 17. Box-and-whisker plots comparing sediment-deposition rates for sediments of the historic (BA) and baseline (AA) 

time-stratigraphic intervals. ................................................................................................................................................. 28 

Figure 18. Scatter diagram showing sediment-deposition rates (sdrAA and sdrBA) versus distance from the river.................... 28 

Figure 19. Cumulative frequency diagram of thickness-weighted average lead concentration in sediments of the historic (BA) 

time-stratigraphic interval.................................................................................................................................................... 29 

Figure 20. Scatter diagram showing thickness-weighted average ppm Pb in sediments of the historic (BA) interval versus 

distance from the Coeur d’Alene River. .............................................................................................................................. 29 

Figure 21. Box-and-whisker plots, comparing interval-weighted average lead (ppm Pb) in sediments of the historic (BA) and 

baseline (AA) time-stratigraphic intervals........................................................................................................................... 30 

Figure 22. Summary plot showing sediment-deposition rates for sediments of BG (background), BA2 (tailings-release), BA1 

(post-tailings-release), and AA (baseline) intervals............................................................................................................. 31 

Figure 23.. Box-and-whisker plots, comparing interval-weighted average lead (ppm Pb) in sediments of the early post-tailingsrelease (BA1) and baseline (AA) intervals .......................................................................................................................... 31 

Figure 24 . Summary plot of lead concentrations (ppm Pb) in sediments of the background (BG) , BAJ (jig), BA2 (tailingsrelease), BA1 (early post-tailings-release) and AA (baseline) intervals.............................................................................. 32 

Tables 

Table 1. Stratigraphic Section of Lead-Rich Sediments from Coeur d’Alene Lake (after Horowitz and others, 1995) ............... 17 

Table 2. Sediment-Deposition Rates and Lead Concentrations, Coeur d’Alene Lake Sediments below and above the 1980 

Volcanic-Ash....................................................................................................................................................................... 19 

Table 3. Baseline Sediment-Deposition Rates for Floodplain Sediments of Interval AA (1980 ~1993)...................................... 22 

Table 4. Baseline Lead Concentrations in Floodplain Sediments of Interval AA (1980 ~1993) .................................................. 23 

Table 5. Baseline Depositional Rates and Lead Concentrations, and Lead in Surface-Sediments of Selected Wetlands............. 25

Table 6. Sediment-Deposition Rates, Medicine Lake Site M92CS............................................................................................... 27 

Table 7. Lead in Lateral-Lake Sediments of Baseline (AA), Post-Tailings-Release (BA1) and Historic (BA) Intervals............. 27 

Table 8. Sediment-Deposition Rates for Paired Baseline and Historic Intervals (sdrAA and sdrBA).......................................... 28 

Table 9. Sediment-Deposition-Rate Ratios for Paired Baseline and Historic Intervals (sdrAA/sdrBA)....................................... 28 

Table 10. Lead Concentrations in Sediments of Paired Baseline and Historic Intervals (PbAA and PbBA)................................ 29 

Table 11. Lead-Concentration Ratios of Paired Baseline and Historic Intervals (PbAA / PbBA)................................................ 30 

Table 12. Lead Concentrations in Sediments of Paired Baseline and Early Post-Tailings-Release Intervals (PbAA and PbBA1)

............................................................................................................................................................................................. 31 

Table 13. Lead-Concentration Ratios of Paired Baseline- and Early Post-Tailings-Release Intervals (PbAA / PbBA1)............. 31

Table 14. Estimated Amounts of Lead-Rich Sediments, and Tonnages of Lead Deposited per Decade during Baseline (AA), 

Historic (BA) and Background (BG) Intervals, Coeur d’Alene River Floodplain .............................................................. 32 

Table 15. Estimated Tonnage of Lead in Sediments on the Floor of the Coeur d’Alene River Valley in about 1993.................. 33 
6 

Table 16. Estimated Tonnage of Lead-Rich Sediment Released Annually by Riverbank Erosion, Coeur d’Alene River, West of 

Cataldo Landing .................................................................................................................................................................. 38 

Table 17. Mean Annual Sediment-Transport Rates in the Coeur d’Alene River (1992-1999), and Baseline Sediment-Deposition 

Rates, Coeur d’Alene River Floodplain, and Coeur d’Alene Lake (1980 ~1993)............................................................... 39 

CONVERSION FACTORS, VERTICAL DATUM, AND WATER YEAR DEFINITION 

Multiply By To obtain 

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) 

foot (ft) 0.3048 meter (m) 

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km) 

inch (in) 2.54 centimeter (cm) 

mile (mi) 1.609 kilometer (km) 

square mile (mi2) 2.590 square kilometer (km2) 

Sea Level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929, which is the reference datum for 

7.5-minute topographic maps of the study area by U.S. Geological Survey. 

Water year: In U.S. Geological Survey reports dealing with surface-water supply, a water year is the 12-

month period, October 1 through September 30. The water year is designated by the calendar year in 

which it ends; thus, the water year ending September 30, 2002, is called the “2002” water year.”
7 

Baseline and Historic Depositional Rates and 

Lead Concentrations, Floodplain Sediments,

Lower Coeur d’Alene River, Idaho 

Abstract 

Lead-rich sediments, containing at least 1000 ppm of lead (Pb), and derived mainly from discarded mill tailings in the 

Coeur d’Alene mining region, cover about 60 km2

 of the 80-km2 floor of the main stem of the Coeur d’Alene River valley, in 

north Idaho. Although mill tailings have not been discarded directly into tributary streams since 1968, frequent floods continue 

to re-mobilize sediment from large secondary sources, previously deposited on the bed, banks, alluvial terraces, and natural 

levees of the river. Thus, lead-rich sediments (also enriched in iron, manganese, zinc, copper, arsenic, cadmium, antimony and 

mercury) continue to be deposited on the floodplain. This is hazardous to the health of resident and visiting human and wildlife 

populations, attracted by the river and its lateral lakes and wetlands. 

This report documents and compares depositional rates and lead concentrations of lead-rich sediments deposited on the 

bed, banks, natural levees, and flood basins of the main stem of the Coeur d’Alene River during several time-stratigraphic 

intervals. These intervals are defined by their stratigraphic positions relative to the base of the section of lead-rich sediments, 

the 1980 Mt. St. Helens volcanic-ash layer, and the sedimentary surface at the time of sampling. Four important intervals 

represent sediment deposition during the following time spans (younger to older): 1. Baseline, from 1980 to about 1993 (after 

tailings disposal to streams ended, but before any major removals of lead-rich sediments); 2. Early post-tailings-release, from 

about 1968 to 1980; 3. Historic floodplain-contamination, from about 1903 to 1968; and 4. Background, before the 1893 flood 

(the first major flood after large-scale mining and milling began upstream in 1886). 

Medians of baseline depositional rates and lead concentrations in levee sediments vary laterally, from 6.4 cm/10y and 

3300 ppm Pb on riverbanks and levee fore-slopes to 2.8 cm/10y and 3800 ppm Pb on levee back-slope uplands. In lateral flood 

basins, baseline medians increase with water depth, from 2.2 cm/10y and 1900 ppm Pb in lateral marshes, to 2.9 cm/10y and 

2100 ppm Pb in littoral margins of lateral lakes, and 4.0 cm/10y and 4400 ppm Pb on limnetic bottoms of lateral lakes. 

The median of lead concentrations in baseline sediments is 82 percent of the median for early post-tailings-release 

sediments, with a 69-percent probability that the two data sets represent statistically different populations. By contrast, the

median of lead concentrations in baseline sediments is 57 percent of the corresponding median for historic-interval sediments, 

and these two data sets definitely represent statistically different populations. The area-weighted average of medians of lead 

concentrations in baseline sediments of all depositional settings is 2900 ppm Pb, which is 1.6 times the 1800 ppm Pb that can be 

lethal to waterfowl. It also is 2.9 times the 1000-ppm-Pb threshold for removal of contaminated soil from residential yards in 

the Coeur d’Alene mining region, and 111 times the 26-ppm median of background lead concentrations in pre-industrial 

floodplain sediments. 

During episodes of high discharge, lead-rich sediments will continue to be mobilized from large secondary sources on 

the bed, banks, and natural levees of the river, and will continue to be deposited on the floodplain during frequent floods. 

Floodplain deposition of lead-rich sediments will continue for centuries unless major secondary sources are removed or 

stabilized. It is therefore important to design, sequence, implement, and maintain remediation in ways that will limit 

recontamination. 

Introduction 

Lead-rich sediments, containing at least 1,000 ppm Pb cover about 61 km2 of the 84-km2 floor of the main stem of the 

Coeur d’Alene River valley (Bookstrom and others, 2001). Large-scale mining and milling of veins enriched in silver, lead, 

zinc, and other metals began in 1886 in the Coeur d’Alene mining region. Beginning in 1886, many mills discarded metallic 

sulfide-bearing tailings directly into streams in the upper drainage basin of the Coeur d’Alene River, and some mills continued

discarding tailings directly into streams until 1968. The discarded tailings washed down-stream, mixed with other sediments in 

transport, and were re-deposited down-valley. 

Frequent floods continue to transport metal-enriched sediment down-valley and onto the floodplain. Thick deposits of 

lead-rich sediments are present in the low-gradient river channel west of Cataldo Landing. These river-channel deposits of leadrich sediments are an important secondary source of lead-rich sediments, vulnerable to transport during floods. Floodwaters 

continue to mobilize and re-deposit lead-rich sediments from this large secondary source, even though tailings have not been 
8 

discarded into tributary streams since 1968, and large volumes of lead-rich sediments were removed from tributary streams and 

floodplains during the late 1990’s. Floodwaters will continue to remobilize lead-rich sediments from the river channel, as well

as from smaller secondary sources along its banks and levees, and will continue to deposit lead-rich sediments in lateral flood

basins, where waterfowl commonly feed, until predominant secondary sources are removed, covered and stabilized, or 

effectively separated from depositional areas on the floodplain. Most of the lead in lead-rich sediments on the floodplain of the Coeur d’Alene River is in forms that are potentially 

bioavailable and toxic to animals (including humans) that might ingest or inhale them in sufficient quantities (Krieger, 1990). 

The biologically based Probable Effect Level for lead in soils or surface sediments is 122 ppm, and the Apparent Effects 

Threshold is 450 ppm, as reported by the U.S. Environmental Protection Agency (USEPA, 1997). The threshold concentration 

of lead in soil to be removed from residential sites in the Bunker Hill Superfund site is 1000 ppm (Richard Martindale, written

communication, 1999). The USEPA Early Action Level for remediation of sediments and soils in common public-use areas is 

2000 ppm Pb (USEPA, 1999). Neufeld (1987), and Audet and others (1999) documented patterns of waterfowl deaths from

lead poisoning in the Coeur d’Alene River valley. In waterfowl feeding experiments, Beyer and others (2000) recognized the 

onset of health injury by lead poisoning from ingestion of 22 percent of sediment, containing 530 ppm Pb, in a diet of rice. At

1800 ppm Pb, feeding experiments by Beyer and others (2000) caused waterfowl to die from lead poisoning. 

Purpose 

The first purpose of this study is to provide a quantitative estimate of post-tailings-release, pre-remedial baseline 

depositional rates and lead concentrations in sediments above the 1980 Mt. St. Helens volcanic-ash layer in various depositional 

settings on the floodplain of the main stem of the Coeur d’Alene River. A second purpose is to compare depositional rates and 

lead concentrations of floodplain sediments deposited before, during, and after large-scale mining, milling, and tailings disposal 

into streams of the Coeur d’Alene mining region. A third purpose is to define spatial and temporal patterns of depositional rates 

in terms of fluvial processes acting on secondary sources of lead-rich sediments, previously deposited along floodwater flow 

paths. A fourth purpose is to predict how estimated rates of fluvial processes, acting on large secondary sources of lead-rich 

sediments along floodwater flow paths, are likely to affect the long-term effectiveness of remediation by various possible 

methods, applied in different depositional settings. 

We present this information, and our interpretations, for the consideration of anyone involved in ongoing efforts to 

plan, apply, and test alternative methods for remediation of environmental hazards, posed by past and continuing deposition of 

lead-rich sediments on the floodplain of the main stem of the Coeur d’Alene River. Such efforts involve workers affiliated with

multiple federal, tribal, state, and local governmental agencies, mining companies, environmental organizations, and 

engineering firms. 

Overview 

We begin with a description the geography of drainage basins involved in the transport and deposition of lead-rich 

sediments. We summarize the history of mining, milling, and tailings management in the Coeur d’Alene mining region. We 

describe the character of lead-rich sediments stored in different depositional settings on the floodplain of the main stem of the 

Coeur d’Alene River. We identify time-stratigraphic markers in the section of lead-rich sediments, and define time-stratigraphic 

intervals between them. We describe our data sets and methods of sample collection and analysis. We present summary 

statistics for sediment-deposition rates and lead concentrations in floodplain sediments, grouped by time-stratigraphic interval 

and depositional setting. We compare summary statistics on rates of deposition and lead concentrations for sediments of 

baseline, historic, and background intervals. We describe processes by which lead-rich sediments, stored in secondary sources 

along floodwater flow paths, are mobilized, transported, and re-deposited during floods. Finally, we summarize our conclusions 

and describe their implications for environmental monitoring, remediation, and restoration. 

Description of Study Area and Surroundings 

The Coeur d’Alene River drains a large part of northern Idaho, from the Idaho-Montana border, to Coeur d’Alene 

Lake, near the border between Idaho and Washington (figure 1). The floodplain of the main stem of the Coeur d’Alene River 

extends from the confluence of the North and South Forks of the Coeur d’Alene River (near Enaville, Idaho) to Coeur d’Alene 

Lake (near Harrison, Idaho, plate 1). The channel of the main stem of the Coeur d’Alene River begins about 3 km (2 mi) 

downstream from the western margin of the Coeur d’Alene mining region (figure 2) and meanders west-southwest to its delta in 

Coeur d’Alene Lake, a river distance of about 56 km (36 mi). 

Figure 1. Location map showing the Coeur d'Alene River system, CdA Lake, and the Spokane River. 

Figure 2. Index and location maps showing the Coeur d’Alene mining region, upstream from the main stem of the Coeur d’Alene River and 

Coeur d’Alene Lake. 
9 

The floodplain of the main stem of the Coeur d’Alene River is about 44 km (27 mi) long, and it averages about 1.9 km 

(1.2 mi) wide. Its surface area is approximately 84 km2

 (32-mi2). We divide the floodplain longitudinally into upper (eastern), 

middle, and lower (western) parts (figure 2). The larger-scale maps in figures 3, 4 and 5 show the boundaries of these floodplain 

segments, and the locations and names of lateral lakes and marshes, tributary streams, towns and settlements. Plates 1 and 2 are 

1:50,000-scale maps of surficial geologic environments on the floodplain of the main stem of the Coeur d’Alene River, with 

colored dots to symbolize baseline rates of sediment deposition, and lead concentrations in sediments deposited on the 

floodplain from 1980 to about 1993. 

Water Levels and Topography 

During summer, the Post Falls dam holds Coeur d’Alene Lake at a nearly constant elevation of 648 m (2125 ft), 

according to the U.S. Geological Survey datum at Harrison, or 649 m (2128 ft), according to the older datum at Post Falls. At 

summer water level (SWL), the pool of the reservoir controlled by the Post Falls dam extends up the Coeur d’Alene River to 

Cataldo Landing, where summer water level in the river also is about 649 m (2125 ft). Natural levees and lateral marshes and 

lakes flank the river (plates 1 and 2). 

Heights of crests of natural levees at 13 surveyed sites vary from a maximum of 4.3 m at Rose Lake to 0.9 m at 

Harrison, with a mean and standard deviation of 2.2 +/-1.0 m (according to spot elevations, surveyed to 0.3 m accuracy by 

Washington Water Power Co., 1980). Levee-crest heights tend to decrease down-valley, but also tend to be relatively high in 

narrow valley segments and on outside margins of meanders. 

Elevations of standing water on the floodplain tend to approach river water level, but may be higher where isolated and 

held, or lower where isolated and pumped. Summer water depths range from 0 to 2 m deep in lateral marshes and littoral zones 

of lateral lakes, and from 2 to about 8 m deep in lateral lakes. Lateral lakes in the mouths of tributary valleys commonly have

steep sides and flat bottoms at depths between about 4 and 8 m (unpub. data, 2000). 

U.S. Geological Survey topographic maps indicate about 914 to 1070 m (3000 to 3500 ft) of vertical relief in the hills 

north and south of the Coeur d’Alene River valley. Elevations of the valley floor rise from about 649 m (2125 ft) at the mouth 

of the Coeur d’Alene River to 655 m (2150 ft) at the confluence of the North and South Forks, 670 m (2200 ft) at Smelterville, 

914 m (3000 ft) at Wallace, and 1040 m (3400 ft) at Mullan. The elevation at Lookout Pass, on the Idaho-Montana border, is 

about 1460 m (4800 ft), which is about 610 m (2000 ft) below the elevation of the highest nearby peak. 

Valley glaciers occupied small cirques and flowed down U-shaped valleys to about the Star-Morning millsite, just 

west of Mullan. West of there, valley cross-sections generally are V-shaped, except where alluvial and lacustrine sediments fill 

the bedrock valley bottom, forming relatively wide and flat alluvial plains. 

About 15,500 to 13,500 years ago, Glacial Lake Coeur d’Alene rose to about the elevation of Kellogg (Dort, 1960). 

Since then, the Spokane River has eroded down through outburst flood gravels from Glacial Lake Missoula that dammed 

Glacial Lake Coeur d’Alene, and the river is incising into bedrock at Post Falls (Alt and Hyndman, 1995). 

The bedrock elevation in the river channel at Post Falls is about 2 m below SWL, which is held constant by the Post 

Falls Dam. During episodes of high discharge, water enters Coeur d’Alene Lake faster than it can exit, even though the gates of

Post Falls Dam are wide open. Coeur d’Alene Lake therefore overfills to elevations as high as about 652 m (2140 ft), which is 

about 4.5 m (15 ft) above SWL. 

Precipitation and Vegetation 

The drainage basin of the Coeur d’Alene River is in a unique inland-forest wet belt on the western slope of the 

Northern Rocky Mountains, with very high average annual precipitation, about 75 to 80% of which is in the form of snow 

(Alan Isaacson, forest hydrologist, oral commun., 2004). Prevailing winds are from the southwest, so that air masses from the 

Pacific Ocean pass northeastward over Coeur d’Alene Lake, rise up the western slopes of the Northern Rocky Mountains, and 

cool adiabatically. As average annual temperatures decrease with increasing altitude, average annual precipitation increases 

sharply from about 41 cm/y (16 in/y) in the valleys and plateaus of eastern Washington to over 122 cm/y (48 in/y) in the Coeur 

d’Alene Mountains (Jackson, 1993). 

On the floodplain of the main stem of the Coeur d’Alene River, riverbanks and levees support redtop grass, alders and 

other shrubs, and trees such as cottonwoods and pines. Seasonal lateral marshes support emergent vegetation, such as grass, 

sedges, common reed, and horsetail reed. Margins of perennial marshes support emergent vegetation, such as cattails, while 

floating plants, such as lily pads are commonly visible in open water. Since the 1968 cessation of tailings disposal into streams, 

lake water has clarified, and plant life, including planktonic diatoms and submergent bottom-rooted plants, such as pondweed, 

have flourished in the shallow open waters of perennial marshes and lateral lakes. 

Lower hillsides are in the Ponderosa Pine Zone, but the hills west of Coeur d’Alene Lake are in the Grand Fir and 

Douglas Fir Zones, where lodgepole pines also are common. Hillsides at moderate elevations are in the Western Redcedar 

Zone, where dominant trees include western redcedar, western hemlock and western white pine, as well as grand fir and 

western larch. Englemann Spruce and Subalpine Fir zones are confined to relatively high elevations along the border between 

northeastern Idaho and northwestern Montana (Frenkel, 1993). 
10 

Deforestation, Runoff and Floods 

Clear-cut logging, road building, forest fires, and surface disturbances resulting from mining, milling, smelting, and 

human habitation in the Coeur d’Alene mining district have resulted in deforestation of many areas in the upper riverine 

subsystem of the Coeur d’Alene-River drainage basin. As a result, the ratio of runoff to precipitation has increased, especially 

since the early 1960’s. Some tributary streams that once ran bank-full or more about twice in 3 years now run bank-full 5 or 6 

times a year. As a result, rates of erosion, sediment-transport, and deposition also have increased, especially along streams in 

the upper part of the Coeur d’Alene drainage basin (Alan Isaacson, oral commun., 2004). 

Flooding is frequent on the floodplain of the Coeur d’Alene River. The first major floods after the onset of mining and 

milling in 1886 were in 1893-94. Between 1893 and 2004, at least 40 discharge episodes peaked at 17,000 f3

/s or more. 

Discharge rates of that magnitude or more cause most of the valley floor to be flooded (S.E. Box, unpub. compilation of data 

from U.S. Geological Survey records, 2000). On average, therefore, much of the valley floor was flooded about every 2.5 y. 

Furthermore, floods with peak discharge of about 70,000 ft3

/s or more have occurred three times in the last 70 years, and twice 

in the last 30 years (in 1933, 1974 and 1996). 

Berenbrock (2002) estimated peak flows at the Cataldo gage at selected recurrence intervals as 18,800 ft3

/s at the 2-y 

frequency interval, 29,400 ft3

/s at the 5-y interval, 37,800 ft3/s at the 10-y interval, 50,000 ft3/s at the 25-y interval, 60,300 ft3/s 

at the 50-y interval, 71,800 ft3

/s at the 100-y interval, 84,500 ft3/s at the 200-y interval, and 104,000 ft3/s at the 500-y interval. 

The U.S. Army Corps of Engineers (USACE, 2001) estimated somewhat higher peak flows at the Cataldo gage at selected 

recurrence intervals: 41,400 ft3

/s at the 10-y frequency interval, 73,500 ft3/s at the 50-y interval, 90,000 ft3/s at the 100-y 

interval, and 136,000 ft3

/s at the 500-y interval. 

Upper Perennial Riverine Subsystem 

Classified according to the Wetlands Classification scheme of Cowardin and others (1979), the upper perennial 

riverine subsystem of the Coeur d’Alene River drainage basin includes all streams of the North- and South-Fork drainage 

basins, and extends down-gradient from the confluence of the North and South Forks to Cataldo Landing (figure 3). The upper 

perennial riverine subsystem has a relatively steep gradient, swift currents, a cobble-gravel bottom, and a braided channel, with 

cobble-gravel bars, gravely riverbanks, and alluvial terraces, topped by sandy to silty floodplain sediments. Downstream from 

mining and milling operations in the Coeur d’Alene mining area, fine-grained sediment in the matrix of the gravel, and sandy to

silty over-bank sediments generally are enriched in metals derived from mining. 

Although tailings-contaminated sediments were deposited on wide alluvial terraces along the South Fork during the 

early history of mining and milling, the South Fork has since incised enough that it generally did not overflow its banks during 

the major flood of February, 1996, except near Osburn and west of Smelterville (figure 2). Downstream from the lower end of 

Smelterville Flats, however, the South Fork overflowed onto its floodplain where it is joined by Pine Creek. The Lower North 

Fork, and the upper main stem of the Coeur d’Alene River completely inundated their floodplains during the major flood of 

1996 (figure 3 and plates 1, and 2). 

Figure 3. Map showing the upper (eastern) part, main stem of the Coeur d’Alene River valley.

Figure 4. Map showing the middle part, main stem of the Coeur d’Alene River valley. 

Figure 5. Map showing the lower (western) part, main stem of the Coeur d’Alene River valley. 

Lower Perennial Riverine Subsystem 

The lower perennial riverine subsystem of the main stem of the Coeur d’Alene River extends from Cataldo Landing to 

Coeur d’Alene Lake (figures 3, 4 and 5). At Cataldo Mission Terraces, the floodplain widens, and the river gradient flattens, 

approaching zero from Cataldo Landing to Coeur d’Alene Lake. Water levels in the lower perennial riverine system and Coeur 

d’Alene Lake are therefore interdependent, and tend to equalize during and after episodes of imbalance between rates of inflow 

and outflow from Coeur d’Alene Lake. 

At Cataldo Landing (figure 3) the upstream gravel bottom gives way to a large friction-dominated central sand bar. 

From Cataldo Landing to Coeur d’Alene Lake, the river occupies a single meandering, sand-bottomed channel, generally about 

60 to 100 m wide and 5 to 15 m deep. Sandy lead-rich sediments, averaging about 3 m thick, cover most of the river bottom, 

especially along relatively straight reaches and in point bars along inside margins of meanders (Figure 6, and Bookstrom and 

others, 2001; Box and others, 2001). 

Figure 6. Block diagram showing features typical of the floodplain of the lower perennial subsystem of the Coeur d’Alene River system, west of 

Cataldo Landing. 
11 

Natural levees flank the river channel, and lateral flood basins flank the levees (figure 6, and plates 1 and 2). From the 

levee crest to the lateral margin of the valley floor, the floodplain surface generally slopes away from levee crests. Therefore, 

most of the valley bottom west of Cataldo Landing is flooded during frequent episodes of high flow, during which water flows 

from the rising river to the floodplain through low passes in levees, inundating the floodplain as Coeur d’Alene Lake levels rise. 

Levee fore-slopes face and slope toward the river. Riverbank deposits of lead-rich sediment cover levee fore-slopes, forming 

wedge-shaped deposits that thicken toward the river. Steep riverbanks commonly form by lateral erosion of riverbank-wedge 

deposits of iron-oxide-cemented lead-rich sediment (figure 6). Levee back-slopes face and slope away from the river, and 

toward lateral flood basins. 

 According to the wetlands classification system of Cowardin and others, 1979, lateral wetlands that are seasonally to 

perennially water-saturated, but are less than 2 m deep at summer water level are classified as palustrine. Larger water bodies 

(at least 8 ha or 20 acres) that are more than 2 m deep are classified as lacustrine. The shallow littoral zone extends from the 

lakeshore to the 2-m depth contour (at summer water level). The deeper limnetic zone includes areas with lake-bottom depths 

greater than 2 m at summer water level. On the floodplain of the Coeur d’Alene River, 11 lateral lakes occupy relatively low 

parts of lateral flood basins, which commonly are at the mouths of tributary side-valleys. Bookstrom and others (1999) mapped 

littoral and limnetic zones in lateral lakes. The lateral lakes generally have relatively flat bottoms at maximum depths of less 

than about 8 m (unpub. data, 1999). 

Distributary channels connect the river with most lateral lakes and some lateral marshes. Natural levees generally flank 

distributary channels, forming riparian levee-uplands (figure 6). Tributary streams commonly flow into the distal margins of 

lateral lakes and marshes (plates 1 and 2). 

Near the mouth of the Coeur d’Alene River, low natural levees flank the river where it traverses the Harrison Arm of 

Coeur d’Alene Lake, and flows into the St. Joe Arm of Coeur d’Alene Lake (figure 5). From the crest of the river-mouth bar, 

the Coeur d’Alene River delta-front slopes to the bottom of the deeper St. Joe Arm of Coeur d’Alene Lake. From the base of 

the delta-front slope, the proximal toe of the delta flattens, thins, and merges with the distal floor of Coeur d’Alene Lake. 

Coeur d’Alene Mining Region 

The western edge of the Coeur d’Alene mining region lies about 3 km (2 mi) upstream from the study area. From 

there, it extends about 50 km (3 to 30 mi) eastward, within the upper perennial subsystem of the Coeur d’Alene River drainage 

basin. Most of the significant mines and mill-sites of the Coeur d’Alene mining region are within the South Fork drainage 

basin, but several are in the southeastern part of the North Fork drainage basin. One mine and mill were in the French Creek 

drainage basin, which joins the main stem of the Coeur d’Alene River near Kingston (figure 3). 

History of Production of Ore, Lead, Zinc, and Silver 

The Coeur d’Alene mining region has produced about 7 million metric tons (Mt) of lead, 3 Mt of zinc, and 30 

thousand tons (kt) of silver (Long, 1998a). According to criteria by Singer (1995), this places the Coeur d’Alene mining region

among the top 1 percent of Ag producers, the top two percent of lead producers, and the top five percent of zinc producers in 

the world (Long and others, 2000). Thirty mines in the Coeur d’Alene region each produced at least 30 kt of lead, 50 kt of zinc, 

or 85 kt of silver (Bookstrom and others, 1996; Long and others, 2000). Those mines are considered significant producers, 

according to the criteria of Singer (1995), who showed that over 99 percent of world production comes from deposits with 

metal resources at least this large. In addition to large mine-mill complexes associated with these 30 significant deposits, over 

100 smaller mines are widely scattered in the Coeur d’Alene mining region. 

Ore deposits in the Coeur d’Alene mining region typically consist of steeply plunging ore shoots within steeply 

dipping veins, which commonly extend to great depths of 2 km or more below the surface. The veins contain quartz and siderite 

(iron carbonate) with varying amounts of galena (silver-bearing lead sulfide), sphalerite (cadmium-mercury-bearing zinc 

sulfide), and tetrahedrite (silver-bearing copper-antimony sulfide), as well as other, less economically important but 

environmentally significant minerals, such as pyrite (iron sulfide), chalcopyrite (copper-iron sulfide), and arsenopyrite (ironarsenic sulfide). Fryklund (1964) noted that the sphalerite and tetrahedrite of the Coeur d’Alene mining district also contain 

traces of mercury. 

Large-scale mining and milling began in 1886, and increased to its first peak during World War I, at 3.2 Mt/y in 1917 

(figure 7a). After the war, ore production decreased to about 1.3 Mt/y in 1923, and then rose to about 2 Mt/y in 1929. After the 

stock market crashed in 1929, ore production decreased to 1 Mt/y during the Great Depression, from 1933 to 1935. Ore 

production increased during the build-up toward World War II, and by the end of the war, ore production had reached 2.75 

Mt/y. After the war, production continued to increase, peaking at 3.2 Mt/y in 1948. During the cold war, ore production 

fluctuated mostly in the range 1.5 +/- 0.3 Mt/y, after which it has generally declined to between 0.4 and 0.7 Mt/y during the era 

of relatively free world trade. 

Large-scale lead production peaked at a rate of185 kt Pb/y in 1917, as World War I ended (figure 7a). Since 1917, lead 

production has generally declined in a descending pattern of short-term fluctuations with peaks at 140 kt Pb/y in 1929, 100 kt 

Pb/y in 1943, and 80 kt Pb/y in 1965. Since 1980, lead production has fluctuated between about five and 50 kt Pb/y. 
12 

Zinc was not recovered until 1905, so tailings produced before 1905 generally contained high concentrations of 

sphalerite. Zinc production rose to about 40 kt Zn/y in 1917, decreased in the early 1920s, and then increased to a maximum of 

80 kt Zn/y during World War II, when pre-1905 tailings at several locations were re-processed to recover zinc. 

Silver in galena was recovered from the start, and silver production briefly reached 370 t Ag/y in 1914. Silver-rich 

tetrahedrite veins of the “Silver Belt” portion of the region went into production during the 1920’s and 1930’s. As indicated in 

figure 7a, silver production exceeded 340 t Ag/y from 1936 to 1942, from 1950 to 1976, and in 1989-90. Since about 1980, 

world production of silver as a byproduct of open-pit gold and copper mines has held silver prices down, and has rendered 

economically marginal the relatively high-cost recovery of silver from deep underground mines of the Coeur d’Alene region. 

Figures 7a and 7b. Graphs showing annual production of ore, lead and zinc, and production-related events (7a) tailings-related events 7b). 

History of Tailings Production 

To recover silver, lead and zinc, mills in the Coeur d’Alene mining region produced about 109 Mt of crushed and 

pulverized mill tailings, containing over 1 Mt of lead and 1 Mt of zinc. Prior to 1968, approximately 56 Mt of tailings 

containing an estimated 800 kt of lead were discarded directly into streams that are tributary to the main stem of the Coeur 

d’Alene River (Long, 1998b). 

Large-scale milling began in 1886 at the Bunker Hill mine. Early milling of high-grade ores, using gravity jigs, 

recovered only 50 to 85 percent of the lead in ores, losing the rest to tailings, which were “flumed” into adjacent streams. Jigs 

are essentially mechanical panning devices, which depend on gravity to separate relatively high-density ore minerals from 

relatively low-density gangue (waste) minerals in agitated water. Settling velocities depend not only on particle density, but 

also on particle size, and jaw crushers and crushing rolls, which were used to crush the ore, produced a wide range of particle

sizes. The majority of particles were coarse to middling, but the rest were fine- to very fine-grained. The powdered particles 

formed slimes in water, and would not settle. Jig slimes with very high concentrations of ore minerals were discarded directly 

into streams, while coarser jig tailings accumulated along the streamside near the mills, to be washed down-valley during spring 

runoff episodes. Ores of the Bunker Hill deposit near Kellogg (the largest producer of the region) were relatively coarsegrained, and by 1937 the Bunker mill was achieving better than 85-percent recovery of galena by sorting crushed ore by grainsize, and using jigs, vibrating tables and related devices (Long, personal communication, 2002). 

Ores of the Morning mine near Mullan (the second-largest producer) were fine-grained, so the Morning mill obtained 

less than 65-percent recovery of lead using jigs and other gravity-separation devices. The slime fraction of jig tailings from the 

Morning mill (and most other jig mills) was discarded directly into streams, and was rapidly carried away in suspension. 

However, the coarse fraction tended to collect near the mill, which clogged the stream channel, causing local flooding of 

alluvial terraces. 

The Morning mill installed flotation equipment to recover sphalerite from slimes in 1911-1912 (Long, 2001). Over the 

next few years other mills installed flotation equipment to recover galena- and sphalerite-bearing slimes from gravity-separator 

tailings. In the flotation process, frothing agents are added to a highly fluid mixture of water and finely-ground ore particles, 

and compressed air is forced up through the slurry to form oily bubbles. Metallic sulfide ore minerals cling to rising oily 

bubbles, but other minerals sink. Rising bubbles carry ore-mineral particles to the surface, where they are collected and dried to 

produce an ore-mineral concentrate. By the late1920’s most mills had abandoned jigs and were fine grinding all the ore to be 

treated by the flotation process (Earl Bennett, personal communication, 1996). By the late 1930’s flotation mills were achieving 

over 85-percent recovery of ore minerals, and the Bunker mill converted to flotation shortly before World War II (Keith Long, 

personal communication, 2002). 

During World War II, about 5 Mt of jig tailings and tailings-bearing sediments were excavated and reprocessed at 

several locations, including Osburn Flats, and the Sweeney mill, near Kellogg. About 75 percent of the Zn, 65 percent of the 

Ag, and 50 percent of the lead in those materials was recovered (Long, 1998b). Tailings from reprocessing were either returned 

to dumps, or discarded into the South Fork. By the late 1950s, flotation mills were achieving over 95-percent recovery of lead 

and silver. 

History of Tailings-Management Practices 

Milling began in 1886, and from the start most tailings were flumed directly to the adjacent streams. Most mills were 

located in the narrow bottoms of V-shaped valleys, with little space for tailing impoundments. In 1901 a tailings dam was built

across the South Fork at the west end of Smelterville Flats to capture slimes discharged from the Bunker Hill milling complex 

at Kellogg (figure 2). Tailing dams also were built at Osburn Flats on the South Fork, and Canyon Creek. The dams at Osburn 

and Canyon Creek washed out in 1917 (the year of peak lead production) leaving metal-rich jig tailings perched on alluvial 

terraces above the active stream channel. The dam at Smelterville Flats washed out in 1933, leaving thick and extensive 

deposits of metal-rich jig tailings on Smelterville Flats (Long, 1998b). 

The Bunker Hill Company built the first large tailing-settling pond at the present site of the Bunker (Central) 

Impoundment Area near Kellogg in 1928 (Long, 1998b). Subsequent tailings were deposited on older jig tailings, which also 

were used to build the impoundment dikes. The Page mill also built a tailings-settling pond farther west on Smelterville Flats. 
13 

In 1932, M.M. Ellis, of the U.S. Bureau of Fisheries found no live fish, and no phytoplankton or zooplankton in the 

waters of the South Fork or the main stem of the Coeur d’Alene River, from above Wallace to the mouth of the river near 

Harrison. He also noted that “The mobility of the mine wastes and mine slimes carried by the Coeur d’Alene River has made 

possible the pollution of considerable lateral areas, as the flats and low lands adjacent to the river, because large quantities of 

these wastes are swept out onto the flats during high water, and left there as the river recedes” (Ellis, 1932, p. 23). Ellis also 

noted that “the small particles of ore together with various other substances in these mine wastes, when exposed to the joint 

action of air, light and moisture can produce a whole series of new compounds some of which may affect aquatic life quite 

differently from the mine wastes as originally poured into the stream” (Ellis, 1932, p. 29). 

After visiting the Sullivan Mills, in British Columbia, Ellis (1932) wrote that they processed similar tonnages of 

similar ore, but had perfected a settling basin system that provided a practical solution for waste disposal without stream 

pollution. Since the many mills of the Coeur d’Alene region were scattered over a wide area, and most were in narrow canyons, 

many continued to discard mill wastes directly into streams. 

Rather than build pipelines to transport tailings to relatively wide, flat areas, the mine owners installed a suction 

dredge to remove tailings-contaminated sediment from the river at Cataldo Landing. The dredge operated during summers from 

1932 to 1967 (Long, 1998b, Grant, 1952). It removed sandy metal-enriched slurry, and pumped it to Cataldo Flats and Mission 

Flats, where the sediment was deposited to form about 7.5 to 10 Mm3

 of dredge spoils, containing about 44 to 69 kt of lead 

(Bookstrom and others, 2001). 

Each summer the dredge removed from the dredge pond an amount of sediment equivalent to the amount of tailings 

produced in the preceding year (William C. Rust, oral commun., 2004). However, the lead content of the sediment removed 

was much less than that of the tailings released. The sediment removed was mixture of tailings-contaminated sediment from the 

South Fork, and uncontaminated sediment from the North Fork. A large percentage of relatively fine-grained tailings-rich 

sediment did not settle at the dredge pond, but was transported in suspension, to be deposited farther down-valley. Especially 

thick and lead-rich deposits of tailings-contaminated sediments formed in the river channel along the Dudley reach, which 

extends from the downstream margin of the dredge pond to the Town of Rose Lake. 

In 1949 the Dayrock mine in Ninemile Creek began using the sand fraction of their tailings as underground backfill, a 

practice that was adopted by most of the other mines from 1954 to 1961 (Long, 1998b). This halved the amount of finer-grained 

tailings and slimes to be discarded, so that construction of settling ponds in the relatively narrow valley bottoms of the mining 

region became feasible. Nevertheless, until 1968, some mills continued to discard tailings and slimes directly into creeks, so 

that the South Fork continued to run “the color of ‘dirty dough’” (Rabe and Flaherty, 1974). Finally, in 1968, the Clean Water 

Act forced all operating mills to impound their tailings in settling ponds (Long, 1998b). 

Data Sets and Methods 

Data sets used in this report include those compiled from previous reports by Bender (1991), Rabbi (1994), Hoffmann 

(1995), Horowitz and others (1995), Fousek (1996), and Box and others (2001). We include additional data on the thickness of 

sediments above the 1980 volcanic-ash layer from Fousek (unpub. data, 1993), and on thickness of lead-rich sediments above 

and below the 1980 volcanic-ash layer from Bookstrom (unpub. data, 1994). 

We compiled relevant data from a total of 148 sites in spreadsheet CdA_SR_PB.xls (appendix 1). Ideally we would 

have data on the thickness and concentration of lead in all lead-rich sediments above and below the 1980 Mt. St. Helens 

volcanic-ash layer at each site. However, not all sites have the 1980 marker layer, and not all sites were exposed, or sampled 

and analyzed for lead to the bottom of the section of lead-rich sediments. Some sites with the 1980 volcanic-ash layer did not 

have lead-rich sediments above or below it. A few sites were outside the study area, but were included for comparison of 

sediment-deposition rates within and outside the study area. 

To represent the characteristics of sediments deposited during a particular time-stratigraphic interval, we used all the 

data available for sediments of that interval. However, to compare sediment-deposition rates or lead concentrations between 

time-stratigraphic intervals, we used only sites with data for both of the intervals to be compared. 

Sampling Strategies 

Fousek (1996) applied a combination of random and systematic sampling strategies. He randomly chose one sample 

location within each systematically defined 1mi2

 Section of land on the floodplain. At each site, he systematically sampled 

intervals from 0-5 cm, 5-15 cm, and 15-30 cm. At sites where 1980 volcanic-ash layer was present, he divided the sample 

interval in which it occurred into subintervals above and below the ash layer. He analyzed these sub-samples for lead and zinc,

and published the results. He also recorded depth to the 1980 volcanic-ash layer, and thickness of the ash layer, but did not 

publish the depth and thickness measurements, which are included here, in appendix 1 (Fousek, unpub. data, 1993). 

Bender (1991), Rabbi (1994), Hoffmann (1995), and Horowitz and others (1995) applied a combination of stratified 

and systematic sampling strategies. By sampling only limnetic lake-bottom sediments, near the central axis of the lake sampled,

they extracted samples from a relatively homogeneous group (or statistical stratum). From each vertical core, they 

systematically sampled continuous strings of 2-cm depth intervals, which also are sediment-thickness intervals, since the 

sediments are layered horizontally. 
14 

Box and others (2001) applied a combination of opportunity and stratified sampling strategies. They sampled sites 

where sections of lead-rich were exposed, or were amenable to sampling by digging, hand coring, or vibro-core drilling. They 

classified sites by depositional environment, and defined sample intervals on the basis of lithologic and stratigraphic 

characteristics. 

Sampling Methods 

Methods of sample-site location, thickness-interval measurement, and sample collection are fully described in reports 

from which data were derived. In general, thickness of horizontally layered sediments was measured vertically downward from 

the surface of sediments composed predominantly of mineral grains at the time of sampling. Low-density surface duff, 

consisting of matted decomposing organic matter, was not included in measurements of thickness of lead-rich sediments, even 

though lead-rich dust or mud commonly coats the organic debris in duff. Samples collected from measured depth intervals were 

chemically analyzed for lead, and the results were used to identify the base of the section of lead-rich sediments (defined as 

sediments containing at least 1,000 ppm Pb). 

 Robert Fousek (unpub. data, 1993) measured the thickness of the 1980 volcanic ash layer and of sediments above it to 

the nearest 1/8th in (0.25 cm), and locally to the nearest 1/16th in (0.13 cm). Most of his cores penetrated only 15 cm, and did not 

reach the bottom of the full section of lead-rich sediments. Below 5 cm his sample interval was 10 cm (from 5 to 15 cm), which 

generally exceeded the thickness of sediments above the ash layer. 

Box and others (2001) and Bookstrom and others (2001) reported thickness of sediments above the 1980 volcanic ash 

layer to the nearest 0.5 cm, and thickness of the ash layer itself to between 0.1 and 0.5 cm. Below the ash layer, they generally 

reported thickness of stratigraphically defined sample intervals to the nearest cm. Most of their sample intervals below the ash 

were thicker than sediments above the ash layer. Many of their measured sections did not reach the bottom of the section of 

lead-rich sediments, especially where sections of lead-rich sediments extend below the water table. 

Bookstrom (unpub. data, 1994) used a field X-Ray fluorescence spectrometer to provide semi-quantitative analyses of 

samples of wet sediments in the field, in order to identify the base of the section of Pb-rich sediments, and measure the 

thickness of that sedimentary section. 

Chemical Analytical Methods 

Methods of sample preparation, digestion, and chemical analysis are fully described in reports from which the data 

were derived. We accepted published data on the concentration of lead in sediments, even though different methods of sample 

collection, sample preparation, digestion, and chemical analysis were used. Box and others (2001) tested the accuracy, 

precision, and inter-laboratory agreement of lead analyses done by 5 laboratories that used a variety of extractions and 

analytical methods. For standards from the National Institute of Standards and Technology (NIST), the most accurate results 

were within 1 percent of the mean of NIST values. For repeated analyses at a single laboratory, the most precise laboratories 

were within 7 percent. For analyses of splits of Coeur d’Alene sediment samples by multiple laboratories, inter-laboratory 

agreement was within 10 to 25 percent. 

Data-Classification and Estimation Methods 

We classified the depositional setting of each sample site as riverbank, upland, palustrine, lacustrine-littoral or 

lacustrine-limnetic. We assigned each sample-depth interval to a time-stratigraphic interval, according to its stratigraphic 

position relative to one or more time-stratigraphic markers, such as the surface at the time of sampling, the 1980 volcanic-ash

layer, and the base of the section of lead-rich sediments. 

To estimate the time-averaged sediment-deposition rate for time-stratigraphic interval at a sample site, we measured 

the thickness of sediment between time-stratigraphic markers, and divided the time-stratigraphic interval thickness (in 

centimeters, to two significant figures) by the time span between deposition of the lower and upper time-stratigraphic markers 

(in decimal decades). We express the average rate of sediment-thickness increase during a time-stratigraphic interval, as the 

average sediment-deposition rate (sdr), in cm per decade (cm/10y, to two significant figures). 

For a sample interval that matches a defined time-stratigraphic interval, the lead concentration of the sample interval 

represents the lead concentration of sediments deposited during the corresponding time-stratigraphic interval. That is the case

for sample intervals that extend from the sediment surface at the time of sampling to the top of the 1980 volcanic-ash layer. For 

any time-stratigraphic interval (tsi) spanning more than one sample interval (si), we calculated thickness-weighted lead 

concentration for sediments deposited during the time interval as 

ppm Pbtsi = si1

(cm * ppm Pb) + si2(cm * ppm Pb) + ...sin / total cmti. 

We retained four significant figures to calculate thickness-weighted average lead concentrations, and summary statistics. 

However, calculation of thickness-weighted average lead concentrations involves multiplication and division of lead 
15 

concentrations by interval thickness, measured to two significant figures. We therefore rounded summary statistics for 

thickness-weighted average lead concentrations, and estimated rates of lead deposition to two significant figures. 

Descriptive Summary Statistics 

We used Microsoft EXCEL to calculate and tabulate descriptive summary statistics and perform student’s t-tests. 

Statistical measures used to describe and compare the data are listed, defined and described briefly as follows, after Spiegel 

(1961), Parratt (1971), Gonick and Smith (1993), and Koch and Link (1970). 

Statistical Definitions 

n = number of sample sites, 

Min to max = minimum value to maximum value (defines the limits of the range or spread in the data), 

Mode = value of the most frequent occurrence (most probable value), 

Mean (experimental arithmetic mean, or average) = sum of values / n, 

(The most important indicator of the central tendency of normal distributions, but sensitive to outliers in 

skewed distributions, and unstable in small populations) 

Standard deviation (stdev) = [(sum of deviations from the mean)2

 / (n – 1)]1/2, 

The standard deviation is the usual estimator of the spread from the mean in normal distributions. The mode, 

median, and mean are coincident in normal distributions, and the data are distributed symmetrically about the 

mean. Approximately 68 percent of the values are within +/- one standard deviation of the mean, and 95 

percent of the values are within +/- two standard deviations of the mean, 

Coefficient of variation (CV) = standard deviation / mean, (ratio of the standard deviation to the mean), 

Peakedness (or kurtosis): a measure of peak height versus peak width, (+) indicates relatively peaked, (-) indicates 

relatively flat, 

Skewness: characterizes the degree of symmetry of a distribution around its mean, (+) indicates a distribution with an 

asymmetric tail extending toward more positive values, (-) indicates a distribution with an asymmetric tail 

extending toward more negative values, 

Geometric mean (geo mean) = antilog of the sum of logs of non-zero values / n, (indicates the central tendency of a 

lognormal distribution, in which most values are small, but a few are very large, and the logarithms of the 

values follow a normal distribution), 

Median (med) = middle value in an odd number of values (ordered by magnitude), or average of two values closest to 

the middle in an even number of values), 

Student’s t-test: statistical test used to determine whether the means of relatively small sample sets are significantly 

different, and represent significantly different populations of data. The probability P(T<=t) depends on the 

relationship of the spreads of the values in the data sets and on the sizes of the sample sets being compared, as 

indicated by the degrees of freedom (df). The populations are assumed to have normal distributions, but the 

test works reasonably well if CV is less than 1.2 (Koch and Link, 1970), and the distribution is approximately 

mound-shaped (Gonick and Smith, 1993). The test is run with the null hypothesis that the two compared data 

sets are the same, which implies that P(T<=t) = 0. If the two data sets are not the same, the test results are 

expressed as a decimal fraction, such as 0.05, which indicates the degree of uncertainty that the two 

populations represented by the data sets are identical. Subtracting this decimal fraction from 1 and 

multiplying by 100 gives the percent-probability that the represented populations are different. If P(T<=t) is 

0.05 or less, the probabilities are 95% to 100% that the populations are different, so they are classified as 

significantly different. If P(T<=t) between 0.05 and 0.25, the probabilities are 75% to 95% that the 

populations are different, so we classify them as probably different. If P(T<=t) is between 0.25 and 0.50, the 

probabilities are 50% to 75% that the populations are different, so we classify them as possibly different. If 

P(T<=t) is between 0.50 and 0.75, the probabilities are 25% to 50% that the populations are different, so we 

classify them as possibly not different. If P(T<=t) is 0.95 or more, the probabilities are 5 percent or less that 

the populations are different, so we classify them as practically no different. 

Statistical Characterizations 

Four tables of summary statistics document sedimentation rates, and five tables document lead concentrations in 

sediments deposited in different depositional settings during different time-stratigraphic intervals. These tables list the summary 

statistics defined above for each sample set that represents sediments deposited in each depositional setting, during a particular 

time-stratigraphic interval, or pair of intervals to be compared. We list the arithmetic mean, geometric mean, and median as 

alternative representations of central tendency. Since most of the data sets have distributions that are intermediate between 

normal and lognormal, none of these statistical indicators perfectly represents the central tendency of the represented 
16 

population. To further characterize distributions, we list peakedness and skewness, although these may be poorly defined in 

small data sets. 

The area-weighted average of the medians of sediment-deposition rates or lead concentrations in different depositional 

settings weights the median for each depositional setting in proportion to the area-fraction of the floodplain that it represents 

(rather than to the number of sample sites in each setting). Bookstrom and others (2001) estimated areas covered by lead-rich 

sediments in each of the following depositional settings as: Riverbed, 7.3 km2

; Riverbank, 2.2 km2; Upland, 14.0 km2; 

Palustrine, 19.6 km2

; Lacustrine littoral, 8.3 km2; and Lacustrine limnetic, 9.6 km2. Thus, lead-rich sediments cover about 61 

km2

 of the 84 km2 of the floor of the Coeur d’Alene River valley, 57.3 km2 of the non-riverine floodplain, and 44.1 km2 of the 

non-limnetic part of the floodplain. 

In tables comparing relatively small data sets with different means, but with standard deviations that overlap, we tested 

whether the means of the two data sets are significantly different by applying a two-tail Student’s t-test, assuming unequal 

variances in the data sets. We compared data from the same interval in different depositional settings, and data from different

intervals in the same depositional setting. 

We use cumulative frequency diagrams to show the cumulative probability of values relative to their magnitudes (as in 

figures 9, 13 and 19). Histograms indicate frequency by class interval (as in figures 11, 12, 15, and 16). Box-and-whisker plots 

(made with the Statview) show the median (50th percentile) at the waist of a box, bounded by the 25th and 75th percentiles, with 

vertical lines extending down to the 10th percentile and up to the 90th percentile, and dots for individual values down to the 

minimum and up to the maximum (figures 17, 21, and 23). 

We cite the mean and standard deviation to characterize the central tendency and the spread, respectively, for most of 

the determinations. According to Koch and Link (1970), the mean is more than 90-percent efficient if the CV is less than 1.2, as 

it generally is for our data sets (See tables). If the standard deviation is greater than the mean (and the minimum is not less than 

zero), we also cite minimum and maximum values to indicate the total range of the spread of values. 

Statistically Based Estimates 

We use the median as a conservative indicator of the central tendency for purposes of estimating volumes and 

tonnages of lead-rich sediments deposited, and of tonnages of lead in such sediments. Unlike the arithmetic mean, the median 

(or 50th percentile) is not much affected by relatively rare and extreme values in small data sets. The median generally is very 

close to the geometric mean, and is a more commonly used and widely understood indicator of the central tendency than the 

geometric mean. 

The mean may be strongly affected by relatively rare and extreme values, especially in relatively small data sets. 

Nevertheless, we use the arithmetic mean of annual rates of bank-retreat to generously estimate the average annual tonnage of 

bank sediments mobilized by bank erosion. 

Stratigraphy of Unconsolidated Sediments 

Pre-Industrial Sediments 

Pre-industrial sediments in the valley of the main stem of the Coeur d’Alene River are unconsolidated fluvial and 

lacustrine sediments of Pleistocene to Holocene age that contain less than100 ppm Pb. The thickness of pre-industrial 

sediments along the deep axis of the bedrock valley increases down-valley. Norbeck (1974) used drill holes and geophysical 

data to estimate that the maximum thickness of pre-industrial sediments in the Coeur d’Alene River valley increases from about 

60 m at a cross-section near Cataldo, to about 130 m at a cross-section between Rose Lake and Killarney Lake. The U.S. Army 

Corps of Engineers (1952) drilled three holes to investigate a proposed dam site near Springston. The deepest hole penetrated 

about 120 m of sand, silt and clay, but failed to reach bedrock. 

Background Sediment-Deposition Rates (sdrBG) 

In the central part of Killarney Lake, 600 cm of pre-industrial organic silt was deposited during about 6700 y at a timeaveraged rate of 0.9 cm/decade. A drill core from the central part of Killarney Lake recovered 50 cm of metallic-organic silt 

(deposited during the mining era) deposited on 600 cm of pre-industrial organic silt, overlying 30 cm of Mazama volcanic ash 

(Sprenke and others, 2000). Bacon (1983) reported an isotopic age determination of 6730 +/- 40 y for the Mazama volcanic ash. 

Thus, the average background rate of sediment deposition in Killarney Lake was 0.9 cm/decade from about 6700 years ago to 

about 100 years ago. 

Background sediment-deposition rates in lateral marshes and levee back slopes probably were similar to those in 

lateral lakes (about 0.9 cm/decade). However, background sediment-deposition rates may have been up to twice as high along 

riverbanks (about 1.8 cm/decade). Nevertheless, riverbanks comprise only about 4 percent of the total floodplain area, so the 

area-weighted average of background sediment-deposition rates for the entire floodplain probably was about 1 cm/decade. 
17 

Background Lead Concentrations (PbBG) 

For a set of 233 samples from 92 samples taken from below the section of lead-rich sediments, and containing less 

than 100 ppm Pb, we calculated the following summary statistics for background lead concentrations (PbBG) in sediments 

deposited before mining-derived sediments from the Coeur d’Alene mining area began to be deposited in the lower Coeur 

d’Alene River valley. 

Minimum of PbBG, 4 ppm Pb, 

Maximum of PbBG, 97 ppm Pb, 

Mode of PbBG, 17 ppm Pb, 

Mean +/- standard deviation of PbBG, 31 +/- 19 ppm Pb, 

Median of PbBG, 26 ppm Pb. 

According to Krauskopf and Bird (1995) the global-average abundance of lead in shale is 20 ppm, which is close to the mean 

concentration of lead in sediments of the St. Joe River valley. Abraham (1994) reported lead concentrations ranging from 21 to 

23 ppm Pb in six samples of sediments from the St. Joe River valley, which has no known exposures of Coeur d’Alene-type 

veins, and is unaffected by mining. Results of a Student’s t-test indicate that the mean of lead concentrations in Coeur d’Alene-River background 

sediments is significantly higher than the mean of lead concentrations of sediments in the St. Joe River valley, both of which 

are underlain by predominantly argillitic rocks (metamorphosed shaly rocks) of the Belt Supergroup. The somewhat higher lead 

concentrations in background-era sediments of the Coeur d’Alene River valley probably resulted from weathering and erosion 

of veins exposed in the Coeur d’Alene mining region before mining began. However, the vein-derived component of premining sediments in the Coeur d’Alene River valley was small, because only small volumes of ore minerals were exposed in 

outcropping veins, exposed locally to weathering and erosion, while very large volumes of surrounding host rocks were 

exposed to weathering and erosion throughout the drainage basin. That changed rapidly as large-scale mining selectively 

brought vein material to the surface, to be pulverized, and exposed to oxidation, and down-valley transport. 

The Section of Lead-Rich Sediments (PbR) 

We define the section of lead-rich sediments (PbR) as the part of the stratigraphic section of surficial sediments that 

contains at least 1000 ppm Pb. The base of the section of lead-rich sediments is the base of the lowest sample interval 

containing at least 1000 ppm Pb, and the top of the lead-rich interval is the top of the highest sample interval containing at least 

1000 ppm Pb. Rarely, a sample interval containing less than 1000 ppm Pb is included in the section of lead-rich sediments, if it 

is bracketed above and below by lead-rich sediments, and the thickness-weighted average of the lower-grade interval and the 

overlying interval exceeds 1000 ppm. 

Lead-rich sediments cover about 60 km2

 of the 80 km2 of the surface of the floor of the main stem of the Coeur 

d’Alene River valley (Bookstrom and others, 2001). Most lead-rich surface sediments are highly enriched in zinc and silver, 

and enriched in copper, cadmium, iron, and manganese, relative to median concentrations of those elements in sediments 

outside the area contaminated by mining wastes, or deposited before mining began. Some lead-rich sediment is also highly 

enriched in arsenic, antimony, and mercury (Fousek, 1996, Box and others, 2001). Concentrations of lead are commonly 

highest near the base of the section of lead-rich sediments, and decrease up-section from the basal maximum (figure 8). This 

reflects the history of lead production and milling practices, as summarized in figures 7a and 7b. Maximum lead concentrations 

near the base of the section reflect the early peak in lead production, which occurred when jig tailings with very high 

concentrations of lead (and zinc) were being discarded directly into streams. 

Horowitz and others (1995) described a full section of lead-rich sediments, and reported the results of their analyses 

for lead and Cs isotopes for core H123, which they extracted from the toe of the Coeur d’Alene River delta in Coeur d’Alene 

Lake (table 1). On the basis of time-stratigraphic markers, cesium isotopic age determinations, and the history of tailings 

production and disposal, we divide the section of lead-rich sediments into time-stratigraphic units, as shown in figure 8 and 

table 1, and described below. 

Table 1. Stratigraphic Section of Lead-Rich Sediments from Coeur d’Alene Lake (after Horowitz and others, 1995) 

Time-Stratigraphic Markers 

Time-stratigraphic markers are identifiable stratigraphic beds or layers that were deposited at a known time, or during 

a relatively short time span that is known exactly, or approximately. 
18 

Surface at the Time of Sampling (1991 to 1998) 

We define the surface at the time of sampling as the top of the section of mineral-dominated sediments at the time of 

sampling. To estimate the baseline sediment-deposition rate for a particular site, we measured the thickness of sediment above 

the 1980 layer at that site, and divided that thickness by decades from May of 1980 to the sampling date (to the nearest year, or 

tenth of a decade). Duff, consisting primarily of decomposing plant debris with only a small proportion of sediment commonly 

overlies mineral-dominated sediments, but was not included in measurements of thickness, or in samples of sediments collected 

for chemical analysis. Most sample sites (111 of 131 sites, or 85 percent) were sampled during the summers of 1991 through 

1995, and 71 (or 54 percent) were sampled in 1993. Thus, most sampling was done before South-Fork floodplain remediation 

projects began in late 1995, and before the major floods of 1996 and 1997. However, 20 sites (or 15 percent) were sampled in 

1998 to fill gaps in the spatial distribution of sample sites on the floodplain. 

Mt. St. Helens Volcanic-Ash Layer (1980) 

On May 18, 1980, the Mt. St. Helens volcano (in western Washington) erupted explosively, blasting volcanic ash high 

into the atmosphere (Corcoran, 1985). Prevailing southwest winds carried the volcanic-ash plume east, and tuff particles settled 

to the ground, covering the Coeur d’Alene River valley with a distinctive layer of nearly white ash-fall tuff. Spring runoff had 

peaked twice before the ash fall, but peaked again on May 27, after the peak of the ash fall. Coeur d’Alene Lake fluctuated 

between 0 and 0.6 m (0 and 2 ft) above summer water level as the volcanic ash fell during late May and early June (U.S. 

Geological Survey, 1981). In December of 1980 a significant over-bank flood rose to 3.6 m (12 ft) above summer water level at 

Dudley (AVISTA - Washington Water Power, unpub. data, 1980), variously eroding, re-distributing, and burying 

unconsolidated volcanic ash. 

Where it is preserved on the floodplain of the Coeur d’Alene River, the 1980 Mt. St. Helens volcanic ash forms a 

nearly white layer of microscopic shards of volcanic glass (bubble-wall fragments) and crystals, buried beneath subsequently 

deposited sediments. The 1980 volcanic-ash layer varies in thickness from 0.2 to 4.5 cm, with a mean and standard deviation of 

0.8 +/- 0.7 cm thick (based on measurements at 91 sites). The 1980 volcanic-ash layer contains various proportions of admixed 

metal-enriched floodplain sediment. Thus, lead concentrations in 4 samples from the 1980 layer range from 620 to 1300 ppm, 

and average 1020 ppm Pb (Fousek, 1996, Horowitz and others, 1995). 

Where it was buried and preserved in the stratigraphic section, the 1980 volcanic-ash layer provides a timestratigraphic marker. Sediments below it were deposited before May 18, 1980, and sediments above it were deposited later. The 

ash layer is well preserved in the upper part of the section of sediments at a high proportion of sites along riverbanks and levees. 

However, the 1980 volcanic-ash layer is only locally present in palustrine and littoral settings, and is absent from riverbed 

sediments, and from sediments on limnetic bottoms of lateral lakes. 

A thick layer of duff at many palustrine sites may have inhibited the formation of a distinct ash layer. Where the ash 

layer is present in palustrine and littoral settings, it tends to be relatively thick and diffuse, and is penetrated by networks of 

rootlets. Thus it appears that root-growth progressively disrupts the ash, and mixes it with sediments above and below it. 

Volcanic ash that fell on the river probably was carried away during a late-May peak in spring runoff, or during a flood 

the following December. Volcanic ash that settled to the limnetic bottoms of lateral lakes, probably mixed with water-saturated

diatomaceous ooze, which has collected on lateral-lake bottoms since the water clarified after cessation of tailings disposal to 

tributary streams in about 1968-69 (Hoffmann, 1985). Mixing of volcanic ash into such mobile, water-saturated, organic ooze 

probably prevented the formation and preservation of a distinct layer of 1980 volcanic ash in limnetic zones of lateral lakes. 

Horowitz and others (1995) recorded the 1980 volcanic-ash layer in 8 of 12 gravity cores from Coeur d’Alene Lakebottom sediments, which contained layered sediments both below and above the 1980 layer. Coeur d’Alene Lake is much 

deeper than the lateral lakes, and its bottom sediments evidently are less organic-rich, less water-saturated, less mobile, and less 

subject to disruption than the bottom sediments of shallower lateral lakes. 

Base of Section of Lead-Rich Sediments (~1903) 

Metal-enriched sediments may have begun to be deposited on the floor of the valley of the main stem of the Coeur 

d’Alene River during the floods of 1893 and 1894. These were the first major floods after large-scale milling began in 1886. 

Horowitz (1995) estimated that metal-enriched sediments were first deposited in Coeur d’Alene Lake between 1895 and 1911 

(~1903 +/- 8 y). The 1895 date was calculated on the basis of the time it would take for the full thickness of lead-rich sediments 

to be deposited at the post-1951 rate of sediment deposition. That rate was determined on the basis of the thickness of sediments 

deposited after the 1951 onset of 137Cs fallout from atmospheric nuclear testing, which was detected in drill-core sediments. 

However, sediment-deposition rates probably varied through time. The 1911 date was based on counts of sedimentary 

laminations, presumed to represent annual layers. However, it is more likely that each layer represents a significant discharge

event. Such events may not have occurred every year, but may have occurred more than once in some years. 

In 1903, farmers in the lower valley filed the first of many lawsuits against mining companies, alleging damage from 

upstream disposal of tailings (Long, 2000). This provided the first well-documented claim of serious damage to the floodplain 

of the main stem of the Coeur d’Alene River as a result of upstream tailings disposal. We therefore interpret the base of the 
19 

section of lead-rich sediments in the Coeur d’Alene River valley as an approximate time-stratigraphic horizon, representing the

onset of deposition of lead-rich sediments in about 1903. It probably took the farmers some time to organize their lawsuit, but

they may have sued before lead concentrations widely exceeded 1,000 ppm. We therefore follow Horowitz (1995) in bracketing 

the onset of mining-derived metal deposition between 1895 and 1911. Thus, we estimate that the base of the section of lead-rich

sediments represents an approximate time-stratigraphic horizon, approximately dated as 1903 +/- 8 y. 

Time-Stratigraphic Intervals 

We measure and name time-stratigraphic intervals on the basis of their relationship to the sedimentary surface at the 

time of sampling, the 1980 volcanic-ash layer, and the base of the section of sediments. We start from the top of the section,

because the surface at the time of sampling is known for every section, and depth to the 1980 volcanic ash is known for most 

sections. However, sampling did not reach the base of every section of lead-rich sediments, containing at least 1000 ppm Pb. 

Pre-Remedial Baseline Interval, AA (1980 ~1993) 

The pre-remedial baseline interval (AA) consists of mineral-dominated sediments above the 1980 volcanic-ash layer at 

the date of measurement and sampling (54 percent of which was done in 1993, 85 percent of which was done between 1991 and 

1995, and 15 percent of which was done in 1998). The baseline interval is considered pre-remedial, because most sampling was 

done before sediments were removed from large areas in the South Fork drainage basin, beginning in late 1995. Baseline 

sediment-deposition rates and lead concentrations provide a basis for comparison to previous and subsequent sedimentdeposition rates and lead concentrations. To calculate the baseline rate of sediment deposition for each site, we used the time

span from May of 1980 to the sampling date, rounded to the nearest year. In text, tables and figures, however, we simplify the 

composite time span to that represented by 85 percent of the samples, which is from 1980 to 1993 +/- 2 y, or 1980 ~1993. 

Historic Floodplain-Contamination Interval, BA, (~1903 to 1980) 

 The historic floodplain-contamination interval (BA) consists of sediments below (and deposited before) the 1980 

volcanic-ash layer. Sediments of the BA stratigraphic interval probably were deposited between about 1903 +/- 8y and 1980. 

Thus, sediments of the BA interval were deposited during a time span of about 77 +/- 8 y. Average BA-interval sedimentdeposition rates, calculated on the basis of a 77-y time span, therefore have a relative error of about +/- 10 percent 

Lead concentrations and lithologic characteristics of BA-interval commonly change down-section, so that the BA 

interval can be divided into subintervals, which can be recognized fairly consistently. Since the 1980 volcanic ash provides a 

clear, sharp time-stratigraphic marker, and the BA interval lies below it, we number BA subintervals BA1 and BA2 with 

increasing depth below the 1980 marker layer (which is opposite to the usual geologic practice of numbering stratigraphic units

in the historical order of deposition, from the base of the section upward). 

Early Post-Tailings-Release Subinterval, BA1 (~1968 to 1980) 

In 1968, daily disposal of about 2,200 t of tailings to tributary streams ended (Hoffmann, 1995), and dredging at 

Cataldo Landing stopped. Thus, the daily supply of fine-grained suspended tailings was greatly reduced, but the supply of 

sandy sediment increased, because such sediment was no longer being removed from the river at Cataldo Landing. In response 

to these changes, rates of deposition of sandy sediments nearly doubled at the toe of the Coeur d’Alene River delta in Coeur 

d’Alene Lake, whereas rates of deposition of fine-grained sediments decreased to about 14 percent of historical BA rates at sites 

along the central axis of the lake, north of the delta toe (tables 1 and 2). Meanwhile, in bays of Coeur d’Alene Lake with 

tributaries not connected to the Coeur d’Alene River, rates of deposition of moderately metal-enriched sediment (formed by 

mixing of clean tributary sediment with metal-enriched lake sediment) continued more-or-less unchanged (table 2). 

Table 2. Sediment-Deposition Rates and Lead Concentrations, Coeur d’Alene Lake Sediments below and above the 1980 Volcanic-Ash 

We define the early post-tailings-release (BA1) subinterval to include any sample interval that directly underlies the 

1980 volcanic-ash layer, and is within 10 percent of the thickness of the overlying the AA time-stratigraphic interval. In 

oxidizing environments, sediments of the AA and BA1 intervals tend to be relatively sandy and loose, as compared to 

underlying sediments, which tend to be finer grained, more oxidized, and more consolidated by iron-oxide cementation. 

However, there is no consistently recognizable marker layer at the base of the BA1 interval. Furthermore, we did not define the

BA1 subinterval until after most of sampling had been done, and at most sites the sample interval directly below the 1980 

marker layer is more than 10 percent thicker than the overlying AA interval. Therefore, we have lead-concentration data for the

BA1 subinterval at only 13 sites, eight of which are in oxidizing environments along riverbanks and levees. 

Since the AA and BA intervals both followed cessation of tailings disposal into tributary streams, and both followed 

cessation of dredging, we suggest that decadal sediment-deposition rates probably were similar for sediments of the AA interval

and the underlying BA1 subinterval, unless the histories of flooding for the two intervals were very different. Although the 

flood histories of the AA and BA1 intervals are not identical, they are roughly similar. The 1974 flood, with a peak discharge of 

about 72,000 ft3

/s at Cataldo, was the only major flood during the BA1 subinterval, whereas three smaller floods with peak 
20 

discharges of near 40,000 ft3/s occurred during the baseline interval (S.E. Box, unpublished compilation of USGS stream-gage 

data, 1993). 

If AA and BA1 sediment-deposition rates were similar, and the assigned thickness of the BA1 interval is within 10 

percent of the thickness of the AA interval, then the time span represented by the BA1 interval is within about 10 percent of the 

time interval represented by the AA interval (13 +/- 2 y). Thus, sediments of the BA1 interval probably were deposited mostly 

between about 1967 +/- 2.2 y and 1980, and most sediments of the BA1 subinterval probably were deposited after the 1968 

cessation of tailings-release into streams. 

Tailings-Release Subinterval, BA2 (~1903 to ~1968) 

The tailings-release subinterval (BA2) consists of lead-rich sediments that lie below the BA1 interval. The thickness of 

the BA2 subinterval is defined by the thickness of the BA interval minus that of the BA1 subinterval. There is no timestratigraphic marker layer between the BA1 and BA2 subintervals, but in the oxidizing environments of riverbanks and levees, 

sediments of the BA2 interval tend to contain higher proportions of fines, and tend to be more thoroughly cemented by ironbearing oxides than overlying sediments of the BA1 subinterval and the AA interval. 

Sediments of the BA2 subinterval probably were deposited between about 1903 +/- 8 y and 1967 +/- 2 y, when tailings 

were being released continuously into upstream tributaries in the Coeur d’Alene mining region, and tailings-bearing sediments 

were being deposited on the floodplain of the main stem of the Coeur d’Alene River. Since the BA1 subinterval was sampled at 

only 13 sites, and the base of the section of sediments was not exposed at many of those sites, the thickness and thicknessweighted average lead concentration of the BA2 subinterval can only be estimated for a few sites, one of which is summarized 

in table 1. 

Jig Tailings-Release Sub-Subinterval, BA2J (~1903 to ~ 1918) 

The jig tailings-release sub-subinterval (BA2J) is defined by a zone of very lead-rich sediments, containing 6000 to 

30,000 ppm Pb, which commonly is present at the base of the section of sediments (table 1 and figure 8). The upper boundary 

of the BA2J sub-subinterval is transitional, and therefore difficult to identify closely or consistently. Nevertheless, we interpret 

the BA2J sub-subinterval to represent sediments deposited from about 1903 +/- 8y to about 1918 +/- 6y, when lead production 

was peaking, jig milling was predominant, and most tailings were being discarded directly into streams. 

Flotation Tailings-Release Sub-Subinterval, BA2F (~1918 to ~ 1968) 

The flotation tailings-release sub-subinterval (BA2F) lies above the jig-tailings-release sub-subinterval (BA2J). The 

thickness of the flotation-tailings-release sub-subinterval is that of the BA2 subinterval minus that of the BA2J sub-subinterval 

(table 1 and figure 8). We interpret sediments of the BA2F sub-subinterval to represent sediments deposited from about 1918 

+/- 6y to 1968, when flotation milling was predominant, and some tailings were still being discarded directly into streams. 

Early Metal-Enrichment Interval, EME (~1893 ~1903) 

The early metal-enrichment interval includes discontinuous lenses of metal-enriched sediments that lie beneath the 

section of lead-rich sediments. Metal-enriched sediment may have begun to be deposited on the floodplain of the main stem of 

the Coeur d’Alene River during the major floods of 1893 and 1894, about 8 or 9 years after large-scale mining and milling 

began in the Coeur d’Alene mining region. However, discontinuous lenses of metal-enriched sediments below the section of 

sediments probably were deposited before the 1903 lawsuit, which we interpret to indicate widespread and significant damages 

from deposition of tailings-contaminated sediment on the floodplain of the main stem of the Coeur d’Alene River. 

Alternatively, some occurrences of metal-enriched sediments below the section of sediments may contain metals that 

were chemically leached from the overlying section of sediments, and re-deposited beneath it. Other occurrences of metalenriched sediments below the section of sediments may have resulted from down-hole contamination during sampling. Downhole contamination is likely at sites where samples were collected by drilling underwater, as at the Dudley drill site (figure 8). 

Character of Sediments by Depositional Setting 

The thickness, grain size, and thickness-weighted average lead concentrations of sediments generally decrease with 

increasing distance from the river and its distributary channels. Depositional settings, in which deposited sediments are stored, 

also change laterally, from predominantly subaqueous in the river channel, to predominantly subaerial along the riverbanks and 

levees, to seasonally and perennially subaqueous in lateral marshes, and to predominantly subaqueous in lateral lakes. Figure 8

shows lead-concentration profiles for typical sections of sediments in riverbed, riverbank, lateral-marsh, and lateral lake 

environments. 

Figure 8. Lead concentration profiles for stratigraphic sections of sediments in the Coeur d’Alene River and on its floodplain. 
21 

Riverbed Sediments 

Riverbed sediments contain about 51 percent of the lead in sediments on the floor of the main stem of the Coeur 

d’Alene River valley (Bookstrom and others, 2001). In the lower perennial riverine subsystem, west of Cataldo Landing, 

riverbed sections of sediments commonly have a basal jig tailings-release sub-subinterval with very high lead concentrations, 

between 10,000 and 30,000 ppm Pb. Near Dudley, this basal interval grades upward to a flotation tailings-release subsubinterval of well-layered olive gray, medium-grained sand and silt containing about 10,000 to 14,000 ppm Pb. About an 

upper meter of active bed sediment consists of well-mixed, poorly stratified, light olive gray to olive brown sand, with 

subordinate interstitial silt- and mud-sized particles, and with lead concentrations in the range 3,000 to 6,000 ppm Pb (figure 8). 

Riverbed sediments are water-saturated, and are stored in transitional suboxic to anoxic conditions, with pore water pH 

ranging from 6.3 to 7.0 (Balistrieri and others, 2000). Riverine sediments have Zn/Pb ratios greater than 1 (Box and others, 

2001, in press). Detrital sulfides of zinc, iron, and lead (sphalerite, pyrite and galena) are more common in riverine deposits

(below the zone of annual water-level fluctuation) than in relatively oxidized subaerial deposits on riverbanks and levees 

(Rantala and Hooper, 1996). 

Riverbank and Levee Sediments 

Riverbank-wedge deposits of sediments contain about 4 percent of the lead in sediments on the floor of the Coeur 

d’Alene River valley, and levee back-slope deposits of sediments contain about 10 percent of that lead (Bookstrom and others, 

2001). Lead-rich sediments on riverbanks and natural levees are mostly sand and silt, variably cemented by red, brown, orange, 

yellow and black iron and manganese oxides hydroxides and oxy-hydrides, formed by subaerial weathering of iron-bearing 

sulfide ore minerals, and manganese-bearing sulfide and carbonate minerals, derived from mined veins. Rare detrital sulfide 

grains are severely pitted, indicating that they have been partially dissolved, and “lead occurs in a wide variety of ferromanganese/oxy-hydroxide phases” that typically form “non-stoichiometric and nano-crystalline grain coatings” (Thornburg and 

Hooper, 2001). Zinc is a minor component of complex manganese oxy-hydrides and is strongly partitioned into siliceous ferrihydrite grain coatings. In oxidizing levee sediments, where pore water is weakly acidic due to the oxidation of iron-bearing 

sulfides, zinc is leached and depleted relative to lead. Therefore, sediments on riverbanks and uplands generally have Zn/Pb 

ratios less than 1.0 (Box and others, 2001, in press). 

On the river-facing fore-slope of the levee crest, a wedge-shaped prism of sediments thickens down-slope from the 

levee crest toward the riverbank (figure 6). Above the 1980 volcanic-ash layer, loose, sandy, pale-brown sediment, commonly 

containing 3000 to 5000 ppm Pb tops riverbank sections of blocky, iron-oxide-cemented riverbank sediments. Post-1980 bank 

sediment resembles active riverbed sediment from the upper part of the section of lead-rich sediments stored in the riverbed. 

Like the active riverbed sediment, the post-1980 bank sediment contains detrital grains of sphalerite, pyrite, and galena, and it 

has Zn/Pb ratios of 1 or more, because it has not been long exposed to the oxidizing environment of the riverbank. It represents 

the fraction of the active riverbed sediment that was fine-grained enough to be transported to the surface of the riverbank, and 

coarse-grained enough to be deposited there. Its presence indicates that the surface of the riverbank receives vertical deposition 

of sandy sediment during floods, even as the face of the riverbank is eroded laterally. 

The levee back-slope extends from the levee crest to the lateral marshes and lakes. It slopes gently away from the river 

and the levee crest. Sandy to silty sediment, carried in the lower part of the floodwater column, settles on levee back-slopes in 

order of decreasing grain-size and density. Relatively thick deposits of levee sand form where sand is washed over the levee on

the outer, down-valley margins of meanders. Very thick sand splays form where floodwaters flow through low passes in the 

levee, and spread onto lateral marshes. During floods, oxidized sediments on levee back-slopes may be vulnerable to 

mobilization and transport into adjacent lateral marshes and lakes. 

Palustrine Sediments 

 Palustrine (lateral-marsh) sediments contain about 8 percent of the lead in sediments on the floor of the Coeur d’Alene 

River valley (Bookstrom and others, 2001). Lateral marshes are present along the lower margins of levee back-slopes, and some 

extend into the mouths of some side valleys. In seasonally flooded parts of lateral marshes, sediments are drained and oxidized

during the dry season, but are flooded and reduced during and after winter and spring floods. 

In lateral marshes with emergent vegetation, a mat of duff (decaying organic debris) commonly develops above 

mineral-dominated sediments. Muddy to powdery sediment commonly coats organic debris in the duff, but the percentage of 

sediment in the duff is low. Below the duff layer, sediments generally consist of silty mud that is poorly stratified. In general, 

the concentrations of lead in mud or dust from the duff are similar to those in underlying sediment. The 1980 Mt. St. Helens ash 

layer is recognizable at only a small percentage of palustrine sites, probably because rootlets of abundant surface vegetation 

tend to disrupt the ash layer. 

In perennially water-saturated to subaqueous lateral marshes, sediments are mostly dark gray to black silt and mud, 

indicative of suboxic to anoxic conditions. Detrital metallic-sulfide mineral grains are rare in lateral-marsh sediments, but 

Thornburg and Hooper (2001) identified a wide variety of microcrystalline to amorphous sulfidic-metal bio-coatings with 

various proportions of lead, zinc, copper, and sulfur. They interpreted these as authigenic metallic-sulfidic biochemical 
22 

sediments. Such sediments may form as follows: 1. Oxidized sediments are winnowed from levees and transported to marshes, 

where they are deposited and stored under reducing conditions. 2. Fe and Mn oxy-hydrides are reduced, which releases metallic 

ions. 3. Sulfide ions, produced by sulfate-reducing bacteria, combine with metallic ions to form authigenic biochemical 

metallic-sulfidic sediments. 

Organic peat with very little mineral or metal content commonly underlies the section of sediments in palustrine 

settings. The underlying peat has background lead concentrations and was deposited before tailings-bearing sediments began to 

accumulate in lateral marshes. 

Lacustrine Sediments 

 Lateral-lake sediments contain about 10 percent of the lead in sediments on the floor of the Coeur d’Alene River 

valley (Bookstrom and others, 2001). Lead-rich sediments in lakeshore littoral zones (less than 2 m deep at summer water level)

are similar to those in lateral marshes. However, sections of sediments on the relatively flat bottoms of lateral lakes (generally 5 

to 6 m deep) are different. Rember and others (1993) used a freeze box to recover non-layered, organic-rich, water-saturated 

sediment from the top of the stratigraphic section of sediments in the limnetic zone of Medicine Lake. According to Robert 

Hooper (personal communication, 2003), the non-layered sediment at the top of the lake-bottom section of sediments is 

diatomaceous. It also is homogeneous with respect to lead concentration, as indicated by assays of similar material from other 

freeze-box cores. This non-layered sediment is underlain by metal-enriched silty mud that is finely laminated and compact. 

Drill cores apparently fail to recover the watery diatomaceous ooze at the top of the section, but do recover the compact, 

laminated silt and mud below it. The section of laminated metal-enriched sediments is underlain by non-layered, organic-rich, 

metal-poor mud that accumulated before the deposition of overlying tailings-contaminated sediments. 

Many lateral lakes fill the mouths of side valleys that are tributary to the main-stem valley. Lake shores adjacent to 

levees and marshes slope gently, but lakeshores along the sides of tributary valleys in bedrock slope steeply. Sandy deltas form 

at the mouths of distributary streams, which deliver sediment from the river, and of tributary streams, which deliver clean 

sediment from tributary valleys. Runoff from nearby levees and marshes also supplies sediment to lateral lakes. 

Some lateral lakes, like Bull Run Lake, are close to the river and directly connected to it by one or more short 

distributary channels. Sections of sediments in such settings tend to have very high maximum lead concentrations near their 

bases (figure 8, Bull Run Lake section). Others, like Rose Lake, are far from the river, and are not connected to it by an active 

distributary channel. Sections of sediments in such settings tend to have lower maximum lead concentrations, which commonly 

peak well above the base of the section of lead-enriched sediments (figure 8, Rose Lake section). 

Baseline Depositional Rates and Lead Concentrations 

Baseline Sediment-Deposition Rates, Overall Summary Statistics 

 Baseline sediment-deposition rates measured at 125 sites on the floodplain of the main stem of the Coeur d’Alene 

River vary from 0 to nearly 29 cm/10y, and have an overall mean and standard deviation of 4.7 +/- 4.3 cm/10y. Table 3 lists 

summary statistics for baseline sediment-deposition rates on the floodplain, based on data listed in appendix 1, collected from

sample sites shown on plate 1. The mean and standard deviation for baseline sediment-deposition rates for riverbanks is 6.9 +/-

5.3 cm/10y, as compared to 3.7 +/- 3.8 cm/10y for levee uplands, 2.5 +/- 1.7 cm/10y for palustrine lateral marshes, 2.4 +/- 1.4

cm/10y for littoral zones of lateral lakes, and 3.8 +/- 0.8 cm/10y for limnetic zones of lateral lakes (table 3). 

Table 3. Baseline Sediment-Deposition Rates for Floodplain Sediments of Interval AA (1980 ~1993) 

Results of Student’s t-tests indicate that baseline rates of sediment deposition are significantly higher for the 

population of sites along riverbanks than for the populations of sites in all other depositional settings on the floodplain. Baseline 

rates of sediment deposition on upland levee back-slopes are similar to those on limnetic lake bottoms, but baseline sediments 

on uplands are sandy to silty, whereas those on limnetic lake bottoms consist of organic-rich, and water-saturated slime or 

slurry. Baseline rates of sediment deposition in lateral marshes and littoral zones of lateral lakes are similar, and are lower than 

those on levee back-slopes and littoral lake bottoms.

Baseline sediment-deposition rates are greater than 2 cm/10y at 65 percent of 125 measurement sites, greater than 3 

cm/10y at 50 percent, greater than 5 cm/10y at 30 percent, and greater than 8 cm/10y at 20 percent of those sites (figure 9). 

Local maximum sediment-deposition rates (and local ranges of rates) decrease with increasing distance from the river (figure 

10). Nearly all of the sites with baseline sediment-deposition rates above about 5 cm/decade are along riverbanks or natural 

levees. Baseline sediment-deposition rates, which commonly are greater than 10 cm/decade on riverbank and levee-upland sites 

near the river, generally decrease to less than 5 cm/decade at distances over 500 m from the river. Baseline sediment-deposition 

rates in palustrine and lacustrine settings generally are less than about 5 cm/decade, but range up to about 8 cm/decade at one

palustrine site that is about 450 m from the river (figure 10). 
23 

Figure 9. Cumulative frequency diagram showing baseline sediment-deposition rates (sdrAA) for sediments deposited on the floodplain from 

1980 to about 1993. 

Figure 10. Scatter diagram showing baseline sediment-deposition rates (sdrAA) versus distance (m) from the Coeur d’Alene River. 

The frequency distribution of baseline sediment-deposition rates (sdrAA) for the entire floodplain has a positive 

skewness of 2.28, a mode of 3.9 cm/decade (table 3 and figure 11). The overall distribution of natural logs of sdrAA is roughly

symmetrical, which indicates a lognormal distribution (figure 12). Therefore, the geometric mean of 3.4 cm/decade is a better 

indicator of the central tendency than the arithmetic mean of 4.7 cm/decade. The median of sdrAA is 3.1 cm/decade is close to 

the geometric mean rate, and is a more commonly used indicator of the central tendency. The median of baseline rates of 

sediment deposition along riverbanks is 6.4 cm/decade, as compared to 2.8 cm/decade for upland levee back-slopes, 2.2 

cm/decade for palustrine lateral marshes, 2.9 cm/decade for littoral shores of lateral lakes, and 4.0 cm/decade for limnetic 

bottoms of lateral lakes. The area-weighted average of these medians is 2.9 cm/decade for the floodplain as a whole. 

Figure 11. Frequency diagram of baseline sediment-deposition rates (sdrAA). 

Figure 12. Frequency diagram of natural logs of baseline sediment-deposition rates (ln sdrAA). 

Baseline Lead Concentration, Overall Summary Statistics 

Baseline lead concentrations in lead-rich sediments of the AA interval (PbAA) at 77 floodplain sites (plate 2) range 

from 1100 to 7500 ppm Pb, with a mean and standard deviation of 3400 +/- 1500 ppm Pb, and a median of 3300 ppm Pb (table 

4). Means and standard deviations of PbAA by depositional setting are: 3400 +/- 990 ppm Pb for 20 riverbank sites, 3600 +/- 

1600 ppm Pb for 40 levee upland sites, 2800 +/- 2100 ppm Pb for 9 palustrine sites, 2300 +/- 900 ppm Pb for 5 littoral sites, and 

4100 +/- 1200 ppm Pb for 3 limnetic sites (table 4). Results of Student’s t-tests indicate that the means of PbAA for riverbank 

and upland sites are significantly higher than for littoral sites, and the mean of PbAA for limnetic sites probably is higher than 

for palustrine and littoral sites. About 85 percent of floodplain sites have baseline lead concentrations (PbAA) greater than 1000 

ppm Pb, about 50 percent have PbAA greater than 2700 ppm Pb, and about 15 percent PbAA greater than 5000 ppm Pb (figure 

13). Maximum lead concentrations and ranges of lead concentrations generally decrease with increasing distance from the river, 

but with high outliers in limnetic settings between 700 and 1700 m from the river (figure 14). 

Table 4. Baseline Lead Concentrations in Floodplain Sediments of Interval AA (1980 ~1993) 

Figure 13. Cumulative frequency distribution of baseline lead concentrations (PbAA) in floodplain sediments. 

Figure 14. Scatter diagram showing ppm Pb in floodplain sediments of the baseline interval (PbAA) versus distance from the Coeur d’Alene 

River. 

The frequency distribution for baseline lead concentrations in lead-rich floodplain sediments is positively skewed, with 

a mode of 1800 ppm (table 4 and figure 15). The distribution of natural logs of PbAA in floodplain sediments is negatively 

skewed, which indicates that the distribution is not lognormal (table 4 and figure 16), possibly because the sample set is 

truncated, and includes no samples with less than 1000 ppm Pb. Inasmuch as the distribution is positively skewed, we favor the 

median as an indicator of central tendency for baseline lead concentrations in floodplain sediments. Medians of lead 

concentration in sediments of the baseline interval vary from 3300 ppm Pb on riverbanks to 3800 ppm Pb on levee uplands, 

1900 ppm Pb in lateral marshes, 2100 ppm Pb on littoral margins of lateral lakes, and 4100 ppm Pb on limnetic bottoms of 

lateral lakes. The area-weighted average of the medians for all depositional settings is 2900 ppm Pb (table 4). 

Figure 15. Frequency diagram of baseline lead concentrations (PbAA) in floodplain sediments. 

Figure 16. Frequency diagram of natural logs of baseline lead concentrations (PbAA) in floodplain sediments. 

Baseline Sediments of Various Depositional Settings and Areas 

This section summarizes available data on baseline rates of sediment-deposition, and lead concentrations in sediments 

of the baseline interval for riparian riverbanks of the Coeur d’Alene River, as compared to nearby rivers, for riparian uplands, 

and for selected wetlands and lakes. In wetlands where the 1980 volcanic-ash layer was not found, or where it was found at 

only a single site or a few sites, lead-concentration data for surface sediments, sampled from depth intervals of 0 to 5 cm, or 0 

to 10 cm, are included. In limnetic zones of lateral lakes, where the 1980 volcanic-ash layer was not found, lead concentrations 

from non-layered sediment above laminated lead-rich sediments are interpreted to represent the baseline interval.
24 

Riparian Riverbanks, Baseline Sediments, Main Stem of Coeur d’Alene River 

Means and standard deviations of baseline sediment-deposition rates on main-stem riverbanks (from summer water 

level to levee crest) vary downstream, from 8.5 +/- 6.2 cm/10y for 26 sites along the upper main stem, to 5.3 +/- 3.0 cm/10y for 

9 sites along the middle main stem, and 5.5 +/- 4.0 cm/10y for 12 sites along the lower main stem (table 3 and figures 3, 4, and 

5). Student’s t-tests indicate a 90-percent probability that the data set for the upper main stem represents a population that is 

statistically different from that for the middle main stem, and an 87-percent probability that the data set for the upper main stem 

represents a population that is statistically different from that for the lower main stem. However there is only a 15 percent 

probability that data sets for the middle and lower main stem represent statistically different populations. The median of lead

concentrations in baseline sediments on riverbanks is 3300 ppm Pb, with a minimum of 1800 ppm Pb, and a maximum of 5400 

ppm Pb (table 4). 

Baseline sediment deposition rates are relatively high on point-bar banks along inner margins of meanders, 

intermediate along both banks of relatively straight reaches, and relatively low on cut-banks along outside margins of meanders

(as indicated by summary statistics based on data tabulated and classified in appendix 1, and illustrated in plate 1). For 42 sites 

from Cataldo Landing to Thompson Lake, baseline sediment-deposition rates on riverbanks vary locally as a function of 

position relative to river-channel meanders. The mean and standard deviation of sediment-deposition rates for 12 sites along 

inside (point-bar) margins of meanders is 9.5 +/- 7.1 cm/10y, as compared to 7.6 +/- 4.4 cm/10y for 14 sites along relatively 

straight river reaches, and 5.7 +/- 4.1 cm/10y for 16 sites along the outside (cut-bank) margins of river-channel meanders. 

Student’s t-tests indicate an 88-percent probability that the data sets for inside- and outside-margins of meanders represent 

different populations, and a 76-percent probability that the data for outside margins and straight-reaches represent different 

populations, but only a 56-percent probability that the data for inside margins and straight reaches represent different 

populations. 

Comparison to Baseline Sediments on Banks of nearby Rivers 

Disturbances related to mining in the Coeur d’Alene mining region contribute to abnormally high rates of sediment 

deposition in the Coeur d’Alene River valley, but post-1980 sediment-deposition rates are also high in neighboring river valleys 

where little to no large-scale mining has occurred. We measured a sedimentation rate of 4 cm/10y at a site on a riverbank of the 

North Fork of the Coeur d’Alene River. Relatively little large-scale mining has occurred in the North Fork drainage basin, 

which is much larger than the South Fork drainage basin, where most of the large-scale mines of the region were operated. We 

also measured a sediment-deposition rate of 8 cm/10y at a riverbank site on the lower St. Joe River, at the lower end of a large 

drainage basin where there has been little or no large-scale mining. Average daily discharge rates of the three rivers in 1999-

2000, as reported by Clark (2003) were: 2240 ft3

/s for the North Fork, 2730 ft3/s for the Coeur d’Alene River, and (about 3000 

ft3

/s) for the lower St. Joe River. The ratio of riverbank sediment-deposition rate to discharge rate was therefore 0.0018 for the

North Fork site, 0.0023 for the main stem of the Coeur d’Alene River, and 0.0027 for the lower St. Joe site. Since there has 

been little mining in the St. Joe drainage basin, these comparisons appear to indicate that other disturbances, such as erosion

related to logging, road-building and forest fires are at least as important as mining in causing abnormally high post-1980 

sedimentation rates along the margins of these three rivers. 

Riparian Levee Uplands, Baseline Sediments 

For 23 sites from Cataldo Landing to Thompson Lake, baseline sediment-deposition rates on levee uplands (on the 

flood-basin side of the levee crest) vary locally as a function of position relative to river-channel meanders. The mean and 

standard deviation of sediment-deposition rates for 10 levee-upland sites lateral to (and down-valley from) outside margins of 

meanders is 6.5 +/- 6.4 cm/10y, as compared to 3.4 +/- 2.2 cm/10y for 10 sites lateral to inside margins of meanders, and 1.8 +/- 

0.3 cm/10y for 3 sites lateral to relatively straight river reaches (as indicated by summary statistics based on data tabulated and 

classified in appendix 1, and illustrated on plate 1). Student’s t-tests indicate a 96-percent probability that inside-margin and 

straight-reach rates of sediment deposition are different, a 94-percent probability that outside-margin and straight-reach rates 

are different, and an 82-percent probability that outside- and inside-margin rates are different. The median of lead 

concentrations in baseline sediments of levee uplands is 3800 ppm Pb, with a minimum of 1400 ppm Pb and a maximum of 

6600 ppm Pb (table 4). 

Riparian Distributary Levees and Sand Splays, Baseline Sediments 

Baseline sediment-deposition rates, measured at 6 sites along the levees of distributary streams vary from 0.8 to 3.9 

cm/10y, with a mean and standard deviation of 2.1 +/- 1.3 cm/10y. By contrast, baseline sediment-deposition rates near the 

centers of two sand splays were higher, ranging from 4.6 to 9.2 cm/10y, and averaging 6.9 cm/10y (plate 1 and appendix 1). 

Lead concentrations in baseline sediments at 8 sites on distributary levees and sand splays generally decrease with distance 

from the river, from 5300 +/- 1200 ppm Pb at 200 to 300 m from the river, to 4600 +/- 130 ppm Pb at 300 to 350 m, to 4300 +/- 

3300 ppm Pb at 400 to 500 m from the river, to 1500 +/- 880 ppm Pb at 600 to 700 m from the river (plate 1 and appendix 1). 
25 

Thick sand-splay deposits are common in the middle segment of the floodplain, and probably account for the highly 

variable thickness of baseline-interval sediments on uplands of the middle segment of the floodplain. The CV for sdrAA on 

uplands in the middle segment of the floodplain is high (1.04), as compared to corresponding CVs for the upper floodplain 

segment (0.77) and the lower floodplain segment (0.36). Sand splays form where river water overflows through a low pass in 

the natural levee, spreads onto the floodplain, and deposits sand as it loses velocity. Sand-splay deposits generally are thickest 

and coarsest-grained near the river, and thinner and finer-grained towards their outer edges. 

Wetlands, Palustrine and Littoral Baseline and Surface Sediments 

Table 5 lists overall summary statistics for baseline depositional rates and lead concentrations for sediments from 

palustrine and littoral wetlands, and summary statistics for available data from each of several palustrine and littoral wetlands 

under consideration for remediation, including Lane Marsh South, Medicine Lake, Cave Lake, Bare Marsh, Thompson Lake, 

Thompson Marsh, and Anderson Lake. Summary statistics for individual wetlands include lead-concentration data for surface 

samples. Fousek (1996) routinely sampled from 0 to 5 cm, but also collected sub-samples above and below the 1980 volcanic 

ash, if present. Campbell and others (1999) consistently sampled from 0 to 10 cm. Means of baseline rates of sedimentdeposition are 2.4 cm/10y for littoral, and 2.5 cm/10 y for palustrine areas. At the mean baseline sediment-deposition rate 2.5

cm/10y for palustrine settings, the 5-cm surface samples, collected by Fousek in 1993 would include sediments deposited 

during a 20-y interval beginning in about 1975. At the same depositional rate, the 10-cm samples, collected in 1995 by 

Campbell and others (1999), would include sediments deposited during a 40-y interval, beginning in about 1955. 

Lead concentrations commonly increase down-section, especially in the lower part of the section of lead-rich 

sediments. We therefore expected that 5- to 10-cm samples of surface sediment would have consistently higher lead 

concentrations than samples of the shallower baseline interval at the same sites. However, the mean and standard deviation for 

998 samples of surface sediment from throughout the floodplain is 3400 +/- 3000 ppm Pb (Bookstrom and others, 2001), and 

the mean and standard deviation for 77 samples of sediments of the baseline interval is 3400 +/- 1500 ppm Pb (table 4). Thus, 

the means of the surface-sample and baseline-sample sets are equal, but the CV for surface samples is 0.88, whereas the CV for 

baseline samples is 0.44. This indicates that although the means of the surface-sample and baseline-sample sets are equal, there 

is more variability in the surface-sample set than in the baseline sample set. 

Table 5. Baseline Depositional Rates and Lead Concentrations, and Lead in Surface-Sediments of Selected Wetlands 

Lane Marsh South, Palustrine Baseline and Surface Sediments 

Lane Marsh South is separated from the river by the railroad embankment, which acts as a setback levee that serves to 

inhibit floodwater from transporting lead-bearing sediment to the marsh behind it. At 6 widely scattered sites in Lane Marsh 

South, surface sediments contained an average of about 1600 +/- 1500 ppm Pb (minimum 445 to maximum 4680 ppm Pb), as 

compared to 2800 +/- 2100 ppm Pb for baseline sediments of palustrine settings throughout the floodplain. The ratio of the 

mean of lead concentrations in Lane Marsh South to the mean of baseline lead concentrations for palustrine settings throughout 

the floodplain is 0.57. This indicates that the potential severity of contamination in Lane Marsh South is about 43 percent less 

than average for palustrine settings on the floodplain. However, the maximum lead concentration was 4680 ppm Pb at a site 

south of the gap in the railroad embankment. 

In Lane Marsh North, between the levee crest and the railroad embankment, surface sediments averaged 4900 +/- 1700 

ppm Pb in an area where baseline sediment-deposition rates were relatively high (11 to 21 cm/10y, as compared to 6.9 +/- 5.3 

cm/10y for riverbank wedges, and 3.7 +/- 3.8 cm/10y for levee uplands). Thus, while lessening the severity of contamination 

behind it (in Lane Marsh South) the railroad embankment apparently increased the rate and severity of contamination on its 

river-facing side (in Lane Marsh North). 

Medicine Lake, Littoral Baseline and Surface Sediments 

At Medicine Lake, the palustrine to littoral wetland being considered for remediation includes two sites where post1968 rates of sediment deposition range from 0.5 to 2.9 cm/10y. The mean and standard deviation of lead concentrations in 

surface sediments at seven palustrine and littoral sites around Medicine Lake is 2200 +/- 1200 ppm Pb (minimum 362 to 

maximum 5620 ppm Pb), as compared 2800 +/- 2100 ppm for palustrine sites, and 2300 +/- 900 ppm for littoral sites 

throughout the floodplain). This indicates that baseline sediment-deposition rates and lead concentrations in palustrine and 

littoral areas around Medicine Lake are similar to those in most palustrine and littoral areas on the floodplain. 

Cave Lake, Littoral Baseline and Surface Sediments 

We have no data for baseline sediment-deposition rates in the palustrine and littoral zones of Cave Lake, but mean and 

standard deviation of lead concentrations in eight samples of littoral surface sediments is 440 +/- 560 ppm Pb (minimum 36 to 

maximum 1590 ppm Pb). Although Cave Lake is connected to Medicine Lake by a narrow passage, it is partly isolated from the 

river by a bedrock hill, and is not directly connected to the river by any distributary that is not blocked by the railroad levee. 
26 

Baseline sediment-deposition rates and lead concentrations in surface sediments are therefore low in palustrine and littoral 

zones marginal to Cave Lake. 

Bare Marsh, Palustrine Baseline and Surface Sediments 

Bare Marsh is on the inside (northern) margin of an obtuse 120-degree bend in the river channel, and its upstream end 

is somewhat protected by the nose of a bedrock ridge that reaches the north bank of the river. Nevertheless, the sedimentdeposition rate was 3.1 cm/10y at a site near the upstream end of the marsh, in the transition zone between levee-back-slope and 

palustrine settings. That is similar to the mean rate of 2.5 +/- 1.7 cm/10y for palustrine sites throughout the floodplain (table 5). 

The mean and standard deviation of lead concentrations in surface sediments at 26 scattered sites in Bare Marsh was 

1500 +/- 1600 ppm Pb (minimum 71 to maximum 5870 ppm Pb, with CV = 1.1) as compared to 2800 +/- 2100 ppm Pb for 

baseline sediments of palustrine sites throughout the floodplain. The ratio of the mean of lead concentrations in surfacesediment samples from Bare Marsh to the mean of lead concentrations in palustrine settings is 0.54, but the high maximum 

concentration (5870 ppm Pb), and the large CV (1.1) indicate extreme spatial variation in lead concentrations. Inasmuch as the 

variation of lead concentrations in our baseline sample set is about half of that in the surface-sample set, we expect that baseline 

and future contamination may be less variable than indicated by the surface-sample set. We therefore expect that the area 

selected for cleanup may receive contaminated sediment at about the average rate for palustrine settings, but with lead 

concentrations that average about 54 percent of the mean for palustrine-settings throughout the floodplain, but might range up 

to about the average for levee uplands (3600 +/- 1600 ppm Pb) in the transitional zone from levee back-slope to lateral marsh. 

Thompson Lake, Littoral Baseline and Surface Sediments 

Thompson Lake lies on the northern, outside margin of an acute 65-degree bend in the river. A short distributary 

channel connects the lacustrine part of the Thompson Lake area directly to the river. Most of the palustrine and littoral wetlands 

around Thompson Lake lie north and west of the river, and are vulnerable to floodwater flow, outward and down-valley from 

the western margin of this acute meander bend. By contrast, a relatively small northeastern part of the marsh receives mostly 

uncontaminated sediment from a lateral tributary. 

The only data on baseline sediment-deposition rates in wetlands around Thompson Lake is from a distal littoral site, 

where the baseline rate of sediment deposition was 2.5 cm/10y, which is very similar to the 2.4-cm/10y mean of baseline 

sediment-deposition rates for littoral settings throughout the floodplain. The mean and standard deviation of lead concentrations 

in surface sediments from 20 sites in palustrine and littoral settings of the Thompson Lake area is 4000 +/- 2200 ppm Pb. That 

is 1.4 times the 2800 +/- 2100 ppm Pb mean for palustrine sites, and 1.7 times the 2300 +/- 900 ppm Pb mean for littoral sites 

throughout the floodplain. 

Thompson Marsh, Littoral Baseline and Surface Sediments 

Thompson Marsh lies beside a straight reach of the river, and is separated from the river by a road embankment, built 

along the levee crest. A dike at the east end of Thompson Marsh separates it from Thompson Lake and its surrounding marshes. 

The mean of lead concentrations in surface sediments from 19 palustrine sites in Thompson Marsh is 1400 +/- 1600 ppm Pb, as 

compared to 2800 +/- 2100 ppm Pb for baseline sediments of palustrine settings throughout the floodplain. Thus the mean of 

lead concentrations in surface sediments is 50 percent of the mean for palustrine settings throughout the floodplain. 

Nevertheless, Thompson Marsh is frequently flooded, and lead-rich sediment continues to be deposited there. 

Anderson Lake, Littoral Baseline and Surface Sediments 

Except for a bridged distributary channel at its western end, Anderson Lake is separated from the river by the railroad 

embankment, which is built along the crest of the natural levee, which is relatively narrow. The mean and standard deviation of

lead concentrations in surface sediments at six littoral sites in Anderson Lake is 600 +/ 980 ppm Pb, as compared to 2300 +/- 

900 ppm Pb for baseline sediments of littoral settings throughout the floodplain. However, the moderately high maximum, large 

standard deviation, and high CV (1.63) for lead concentrations in surface-samples indicate a high degree of spatial variability

within the area being considered for remediation. Three areas with relatively high lead concentrations are near the northeastern 

margin of the lake, near a small distributary at the northwestern (down-valley) end of the lake, and near the margins of the 

limnetic lake bottom. 

Limnetic Post-Tailings-Release Sediments 

Because the 1980 volcanic-ash layer is not present in most sections of lead-rich sediments deposited on limnetic lateral 

lake bottoms, alternate approaches were required to estimate the baseline depositional rates or to define the baseline time 

interval. These approaches are described for data from three lateral lakes below. 
27 

Medicine-Lake, Limnetic Post-Tailings-Release Sediments 

Rember and others (1993) dated sediments in freeze-box core M92CS (from Medicine Lake) on the basis of cesiumisotopic activities, measured with a gamma-ray spectrometer. Radioactive 137Cs accumulated in the environment from 1951 to 

1963-1964 as a result of fallout from atmospheric testing of nuclear weapons. After 1963-1964, atmospheric testing of nuclear 

weapons ended, and 137Cs activity in the environment decreased as a result of radioactive decay. 

In freeze-box core M92CS (from Medicine Lake) non-layered, water-saturated, organic-rich sediment above the 10-cm 

depth is underlain silty laminated sediment. Rember and others (1993) identified the 1951 onset of 137Cs accumulation in the 30-

32 cm depth interval, and the 1963-1964-peak in 137Cs activity in the 16-18 cm depth interval. This indicates that 14 cm 

thickness of sediment was deposited in 12.5 y, at an average rate of 1.1 cm/y (or 11 cm/decade). Extrapolation of that 

depositional rate to the 10-cm depth, where laminated sediments are overlain by non-layered sediment, indicates that the change

from layered silty sediment to non-layered organic-rich sediment occurred in about 1969. Thus, the upper 10 cm of non-layered 

sediment accumulated in about 23 y (from 1969 to 1992) at an average rate of 4.3 cm/decade, as compared to the pre-1969 rate 

of 11 cm/decade (table 6). 

Rember and others (1993) credited the cessation of tailings-disposal into streams (beginning in 1968) for the reduction 

in sediment-deposition rate, and the change from laminated silty sediments (deposited before about 1969) to non-layered, 

water-saturated, organic-rich sediments (deposited after about 1969). As the proportion of silty suspended tailings decreased, 

lake water clarified, and sunlight penetrated the relatively shallow waters of lateral lakes, allowing diatoms and other aquatic 

organisms to flourish, and increasing the proportion of organic sediment deposited on lake bottoms. The resulting non-layered, 

water-saturated, organic-rich sediment was too soft and mobile to preserve the 1980 volcanic-ash layer (and too mobile to be 

recovered by conventional core drilling). Nevertheless, the change from layered to non-layered sediment provides a 1969 timestratigraphic marker that can be recognized in other freeze-box cores. If the post-tailings-release rate of sediment deposition is 

assumed constant, the 1.2-decade AA interval occupies the upper 5.2 cm of non-layered sediment, and the baseline rate of 

sediment deposition at site was about 4.3 cm/decade at site M92CS on the bottom of Medicine Lake (table 6). 

Table 6. Sediment-Deposition Rates, Medicine Lake Site M92CS 

Hoffmann (1995) reported lead concentrations for 2-cm sample intervals from freeze-box site M91A, on the 

distributary inlet delta in Medicine Lake, about 300 m northwest of M92CS. In the deltaic setting of site M91A, the upper 8 cm 

of the section was sandy silt, rather than organic-rich sediment. By analogy with the post-1968 increase in sand in core 123, on 

the toe of the Coeur d’Alene River delta in Coeur d’Alene Lake, we interpret the up-section change from silt to sandy silt on the 

distributary delta in Medicine Lake as a time-stratigraphic marker, indicating the ending of sand-dredging at Caltaldo Flats and 

the cessation of tailings disposal into tributary streams, in 1968-1969. 

Assuming relatively consistent rates of sediment deposition after 1968-1969, sediments of the baseline interval occupy 

the top 4 cm of the M91A section, and baseline (AA) and post-tailings (BA1) intervals were deposited at a rate of about 3.6 

cm/decade. The lead concentration in 4 cm of baseline (AA) sediments averages 5200 +/- 1200 ppm, as compared to 5900 +/- 

1200 ppm in the underlying 4 cm of post-tailings-release, pre baseline sediments of the BA1-subinterval. From 4 cm to the 

bottom of the hole at 52 cm, sediments of the BA interval contain an average of 5000 +/- 2000 ppm Pb. The hole bottomed in 

sediments containing 3900 ppm Pb, and did not reach the basal spike in lead concentration (table 7). 

Table 7. Lead in Lateral-Lake Sediments of Baseline (AA), Post-Tailings-Release (BA1) and Historic (BA) Intervals 

Killarney Lake, Limnetic Post-Tailings-Release Sediments 

Bender (1991) reported lead concentrations for 2-cm increments of freeze-box section KF (or 91SBKF2) near the 

middle, deepest part of Killarney Lake, where a full section of sediments was 50 cm thick. No description of the sediments in 

this particular section was published. Nevertheless, we suggest that the 1969 time-stratigraphic horizon can be recognized on 

the basis of a change from sediments at the top of the section, in which lead concentration is consistent, to underlying sediments 

in which lead concentrations fluctuate, and generally increase down-section. Sediments in the upper five 2-cm sample intervals,

which represent the top 10 cm of the section, contain an average of 4200 +/- 220 ppm Pb. The relatively small standard 

deviation (220 ppm) and low coefficient of variation (0.05) indicate that the upper 10 cm of sediment is nearly homogeneous 

with respect to lead concentration. We interpret this to indicate that the upper 10 cm of sediment was deposited after 1969, 

when earlier deposition of layered sediments changed to deposition of homogeneous, non-layered sediments, in response to 

cessation of tailings disposal into tributary streams in 1968. Below the 10-cm depth, lead concentrations fluctuate and increase 

progressively down-section, to a maximum of 37,400 ppm at a depth of 42 to 44 cm. This indicates that sediments below the 10 

cm depth are layered, and can thus be correlated with layered sediments of the BA interval, deposited before about 1969 in the 

dated M92CS section. 

If the upper 10-cm interval of homogeneous sediment was deposited at the KF site after about 1969, and rates of 

sediment deposition were relatively consistent from 1969 to 1991, then about 5 cm of homogeneous sediment was deposited 

during the baseline (AA) interval, from 1980 to 1991. Therefore, the post-1980 baseline rate of sediment deposition (sdrAA) 

was 5 cm in 11 y, or 4.5 cm/decade. Before 1980, about 45 cm of sediment was deposited at the KF site during the 
28 

approximately 77-y historic baseline (BA) interval, at an average rate of 5.8 cm/decade (table 7). Thus, the ratio of sdrAA to 

sdrBA at the KF site is 0.78. 

From 0 to 5 cm of depth, sediments interpreted to represent the baseline (AA) interval contain an average of 4400 +/- 

170 ppm Pb, as compared to an average of 4100 +/- 150 ppm Pb in sediments of the BA1 interval, at 5 to 10 cm of depth (table 

7). Sediments interpreted to represent the entire BA interval extend from 5 to 50 cm deep, and contain an average of 12000 +/- 

9600 ppm Pb. The freeze box sampled to 50 cm deep, and bottomed in sediments containing 600 ppm Pb. 

Thompson Lake, Limnetic Post-Tailings-Release Sediments 

Hoffmann (1995) reported lead concentrations for 2-cm increments of freeze-box section T91A, near the middle and 

deepest part of Thompson Lake, where he sampled a nearly full section of sediments. He published no description of these 

sediments. The upper three 2-cm sample intervals, are nearly homogeneous with respect to lead concentration, and contain an 

average of 2800 +/- 85 ppm Pb, with a very low coefficient of variation (0.03). Below 6 cm, lead concentrations fluctuate and 

increase progressively down-section, indicating layered sediments, with a mean of 7800 +/- 4500 ppm Pb (table 7), and a 

maximum of about 17,000 ppm at the bottom of the 48-cm hole. 

By analogy with the dated section M92CS, we suggest that homogeneous sediments above the 4-cm depth were 

deposited after 1969, and layered sediments below that were deposited before 1969. If sediment-deposition rates were relatively

consistent from about 1969 to 1991, about 3 cm of homogeneous sediment would have accumulated during the 11-y baseline 

(AA) interval, at an average rate of 2.7 cm/10y from 1980 to 1991 (table 7) Before that, the historic (BA) rate of deposition, 

during the 77 y from about 1903 to 1980, was 5.5 cm/decade (or more, depending on how much of the BA interval lies below 

the 48-cm depth reached by the freeze box). 

Depositional Rates and Lead Concentrations through Time 

By comparing depositional rates and lead concentrations of baseline-interval sediments with those of previous timestratigraphic intervals, we can outline trends in sediment-deposition rates and lead concentrations in sediments deposited 

through time, from about 1893 to about 1993. 

Historic and Baseline Depositional Rates 

The historic rate of sediment deposition (sdrBA) is calculated as the thickness (cm) of sediment below the 1980 

volcanic-ash layer, divided by the approximately 7.7-decade duration of the of the BA time-stratigraphic interval, which began 

in 1903 +/- 8 y, and ended in 1980. Historic rates of deposition of sediment on the floodplain average 7.8 +/- 7.3 cm/decade, 

with a geometric mean of 5.2 cm/decade, and a median of 4.7 cm/decade (table 8, middle part). 

Medians of sdrBA by depositional setting are 10 cm/decade for riverbanks, 3.6 cm/decade for levee uplands, 4.0 

cm/decade for palustrine lateral marshes, 3.2 cm/decade for littoral margins of lateral lakes, and 5.8 cm/decade for limnetic 

lateral lake bottoms. The area-weighted average of the medians for all depositional settings is 4.3 cm/decade. Student’s t-tests 

indicate that the mean of sdrBA for riverbank sites is significantly higher than the mean for limnetic sites, and probably is 

higher than the means for upland and palustrine sites (table 8, middle part). 

Summary statistics for sediment-deposition rates for the baseline interval (table 8, upper part) can be compared to 

sedimentation rates for the historic interval (table 8, middle part). The data represent baseline and historic sediment-deposition 

rates for 46 sites where we were able to determine both sdrAA and sdrBA. All indicators of central tendency are lower for 

sdrAA than for sdrBA in all floodplain depositional settings. A series of t-tests indicates that the mean of sdrAA is significantly 

lower than sdrBA for limnetic sites, and also is probably lower for upland settings (table 8). For the floodplain as a whole, there 

is an 87-percent probability that sdrAA is lower than sdrBA. 

Table 8. Sediment-Deposition Rates for Paired Baseline and Historic Intervals (sdrAA and sdrBA) 

Box-and-whisker plots compare distributions of baseline (right) and historic (left) sediment-deposition rates at 46 

floodplain sites (figure 17). Baseline sediment-deposition rates (sdrAA) were lower than historic rates (sdrBA) at the maximum,

90th-, 75th-, and 50th- and 25th-percentile levels of the two populations. For example, the ratio of sdrAA to sdrBA was about 0.77 

at the maximum level, about 0.75 at the 90th and 75th percentiles, 0.77 at the 50th percentile, and 0.67 at the 25th percentile. 

Figure 17. Box-and-whisker plots comparing sediment-deposition rates for sediments of the historic (BA) and baseline (AA) time-stratigraphic 

intervals. 

Figure 18. Scatter diagram showing sediment-deposition rates (sdrAA and sdrBA) versus distance from the river. 

Table 9. Sediment-Deposition-Rate Ratios for Paired Baseline and Historic Intervals (sdrAA/sdrBA) 
29 

A scatter diagram (figure 18) shows rates of sediment deposition for paired sdrAA and sdrBA intervals at 46 sites, 

plotted as a function of distance from the river. Maximum values and ranges of sdrAA and sdrBA are highest along riverbanks, 

and decrease sharply with increasing distance from the river. However, maximum values of both sdrAA and sdrBA increase 

slightly on limnetic lateral-lake bottoms between 500 and 2000 m from the river. At most distances from the river, the highest 

sdrAA values (colored symbols) are lower than the highest sdrBA values (open symbols). At the outermost margin of the 

floodplain, however, lead-rich sediments of the baseline (AA) interval overlap sediments of the historic interval that contain 

less than 1000 ppm Pb, and therefore represent 0 cm of lead-rich sediment. 

Summary statistics indicate that baseline sediment-deposition rates on most of the floodplain generally decreased 

relative to historic rates, but the opposite occurred at about 50 percent of riverbank sites. Summary statistics for the ratio of 

sdrAA to sdrBA at individual sites indicate a median of 1.05, a mean of 1.72 +/- 2.33, and a range of 0.1 to 10.3 (table 9). At 11 

of 22 sites, the ratio of sdrAA to sdrBA was1.05 or more, at one site it was between 0.95 and 1.05, and at 10 sites it was 0.95 or 

less. Reasons for this may include the following: 1. Although cessation of tailings disposal in 1968 reduced the supply of finegrained sediment, it did not significantly affect the supply of sandy sediment to be deposited on riverbanks, 2. Deposition of 

sandy sediment at riverbank sites is dependent on local and temporary variations in flow velocities, which vary according to 

flood histories and changing local channel morphologies, 3. Cessation of dredging at Cataldo Landing allowed increased 

transport of sandy sediment, some of which was suspended and lofted onto riverbanks, but much of which was transported 

down-river, and deposited on the Coeur d’Alene River delta, where baseline depositional rates increased relative to historic 

rates by a factor of 1.86 (table 2). 

Historic and Baseline Lead Concentrations 

The mean concentration of lead in sediments of the historic interval (PbBA) at 28 sites is 5900 +/- 3200 ppm Pb, the 

geometric mean is 4900 ppm Pb, the median is 5400 ppm Pb, and the area-weighted average of medians for all floodplain 

depositional settings is 5800 ppm Pb (table 10, middle part). As indicated by Student’s t-tests, the mean of PbBA for sandy 

riverbank sites near the river may be less than the mean for silty upland sites, and probably is less than the mean for silty mud in 

limnetic sites (table 10, lower part). Thus, the tendency for lead concentrations to decrease with increasing distance from the

river is countered by a tendency for lead concentrations to increase with increasing proportions of finer-grained sediment 

deposited on levee back-slopes, and especially at relatively distal limnetic sites. 

A cumulative-frequency diagram shows thickness-weighted concentrations of lead (PbBA) in sections of the historic 

time-stratigraphic interval at 28 floodplain sites (figure 19). The thickness-weighted average of lead concentrations in sediments 

of the historic interval (PbBA) is greater than 3300 ppm Pb at 80 percent of sites, greater than 5400 ppm Pb at 50 percent, and

greater than 8500 ppm Pb at 20 percent. The sites are coded to indicate depositional setting. At most riverbank sites, the historic 

interval has PbBA between about 3300 and 5500 ppm, and the sediments are sandy to silty. At most levee upland (back-slope) 

sites PbBA is between 5200 and 8400 ppm, and the sediments are relatively silty. Three limnetic sites have PbBA between 

5000 and 12,000 ppm, and most lead-rich sediments are silty to muddy. A scatter diagram of PbBA as a function of distance 

from the river displays widely scattered data points, showing no clear and consistent relationship between thickness-weighted 

average lead concentrations for sediments of the BA interval versus distance from the river (figure 20). 

Table 10 lists summary statistics for concentrations of lead in sediments of the baseline and historic intervals at 28 

sites where both complete intervals have been analyzed for lead. All indicators of the central tendency of PbAA are lower than 

corresponding indicators for PbBA. The mean of PbAA for the 28 sites is 3100 +/- 1700 ppm, as compared to the 5900 +/- 

3200-ppm mean of PbBA. Thus, the ratio of the means of PbAA to PbBA is 0.53. A Student’s t-test confirms that the mean of 

PbAA is significantly lower than the mean of PbBA for the floodplain as a whole (table 10, bottom). The box-and-whisker plots 

in figure 21 show that baseline lead concentrations (PbAA) are clearly lower than historic PbBA at a range of percentile levels. 

The ratio of the median of PbAA to the median of PbBA is 0.57, and the average of the ratios of PbAA to PbBA at the 

maximum, 90th, 75th, 50th, and 25th –percentile levels is 0.52. 

The mean of baseline to historic lead-concentration ratios (PbAA/PbBA) for 28 floodplain sites is 0.71 +/- 0.38, and 

the median is 0.72 (table 11). The area-weighted average of medians of PbAA/PbBA by depositional setting is 0.61. As 

indicated by Student’s t-tests, the mean of PbAA/PbBA ratios for riverbanks (0.84 +/- 0.26) probably is greater than the 

corresponding mean for levee-uplands (0.66 +/- 0.39), and may be greater than the mean for limnetic deposits (0.59 +/- 0.39). 

This indicates that baseline lead concentrations decreased less (relative to historic concentrations) at sandy riverbank sites than 

at silty levee upland sites, and less at riverbank and upland sites than at limnetic sites, typified by a change from historic 

laminated silt and mud to baseline organic-rich, water-saturated ooze. 

Table 10. Lead Concentrations in Sediments of Paired Baseline and Historic Intervals (PbAA and PbBA) 

Figure 19. Cumulative frequency diagram of thickness-weighted average lead concentration in sediments of the historic (BA) timestratigraphic interval. 

Figure 20. Scatter diagram showing thickness-weighted average ppm Pb in sediments of the historic (BA) interval versus distance from the 

Coeur d’Alene River. 
30 

Figure 21. Box-and-whisker plots, comparing interval-weighted average lead (ppm Pb) in sediments of the historic (BA) and baseline (AA) 

time-stratigraphic intervals. 

Table 11. Lead-Concentration Ratios of Paired Baseline and Historic Intervals (PbAA / PbBA) 

Although tailings disposal to tributary streams stopped in 1968, secondary sources of lead-rich sediments, previously 

deposited along floodwater flow paths continue to be mobilized during floods, and mixed with relatively uncontaminated 

sediments from tributaries largely unaffected by mining. Inasmuch as PbAA is lower than PbBA at 71 percent of 28 sites, and 

the ratio of the medians of PbAA and PbBA is about 0.52, the proportion of contaminated to uncontaminated sediments in the 

overall mix has tended to decrease since about 1968. 

Early Post-Tailings-Release Depositional Rates (sdrBA1) 

We defined the early post-tailings-release (BA1) subinterval as the uppermost subinterval of the historic BA interval, 

with thickness within 10 percent of the thickness of the overlying AA interval. Only 13 sample sites had a sample interval that

fit this definition. We make the simplifying assumption that at any particular site, the time-averaged rates of sedimentdeposition for the two post-tailings-release intervals (sdrAA and sdrBA1) were similar enough to be considered sub-equal. If 

sediments of the successive BA1 and AA intervals were deposited at sub-equal rates, they also were deposited during time 

spans of sub-equal duration. Since sediments of the AA interval were deposited during a time interval of about 13 +/- 2 y after

1980, we assume that sediments of the BA1 interval were deposited during a time interval of about 13 +/- 2 y before 1980 (or 

between about 1967 +/- 2 y and 1980). 

Cessation of direct disposal of tailings into upstream tributaries, and cessation of dredging at Cataldo Landing 

occurred in about 1968, and presumably would have affected both post-1967 intervals more-or-less equally. However, since 

sediment transport increases geometrically with increasing discharge, the major flood of 1974 probably caused an episode of 

very high rates of sediment-transport and deposition during the BA1 time interval. That deposition may not have been fully 

compensated by deposition caused by three smaller floods during the AA interval. Thus, sediment in the BA1 interval may have 

been deposited in a somewhat shorter time interval than the sub-equal thickness of sediment in the AA interval. Thus, the time 

interval represented by the BA1 interval is likely to be shorter, rather than longer than 13 y, and deposition of the BA1 interval 

is more likely to have begun after than before 1967, possibly in about 1968. 

Tailings-Release Depositional Rates (sdrBA2) 

Sediments of the tailings-release (BA2) subinterval probably were deposited between about 1903 +/- 8 y and about 

1968. If it took about 7.7-decades for deposition of BA-interval sediments, and about 1.2-decades for deposition of BA1-

interval sediments, then sediment-deposition for the BA2 interval can be approximated according to the equation: 

sdrBA2 = (sdrBA*7.7 decades) – (sdrBA1*1.2 decades) / 6.5 decades. 

Substituting summary statistics for BA and BA1 intervals into this equation yields the following estimated summary 

statistics for BA2 sediment-deposition rates: sdrBA2 ranges from 0 to 36 cm/decade, with a mode of 3.5 cm/decade, a mean 

and standard deviation of 8.2 +/- 7.6 cm/decade, a geometric mean of 5.4 cm/decade, a median of 4.9 cm/decade, and an areaweighted average of medians for depositional settings of 4.3-cm/decade. 

Figure 22 shows summary statistics for floodplain sediment-deposition rates during successive time-stratigraphic 

intervals. Before large-scale mining began in 1886, the background rate of sediment deposition on the floodplain of the main 

stem of the Coeur d’Alene River probably was about 1 cm/decade. From 1886 to 1968, mill tailings were discarded into the 

South Fork of the Coeur d’Alene River and some of its tributaries. Tailings-bearing sediments probably began to be deposited 

on the floodplain of the main stem of the Coeur d’Alene River during the major floods of 1893 and 1894. 

From about 1903 to about 1968, tailings-bearing sediments of the BA2 time-stratigraphic interval were deposited on 

the floodplain of the main stem of the Coeur d’Alene River. The median of time-interval-averaged sediment-deposition rates for 

the BA2 interval is 4.9 cm/decade, which is nearly almost five times the background rate. 

Sediment-deposition rates probably peaked during the winter flood of 1933. From about 1932 to 1967 a dredge 

removed sand from the river channel at Cataldo Landing every summer. River dredging after 1932, decreasing production after 

1945, and increasing underground placement of sandy tailings after 1950 combined to decrease the supply of tailings-bearing 

sediment. 

Nevertheless, about 2,200 t of tailings were still being discarded daily into the South Fork and some of its tributaries 

until 1968, when tailings disposal into streams was disallowed. After 1968, the median of floodplain sediment-deposition rates 

decreased to the baseline rate of 3.6 cm/decade, which is about 73 percent the median of rates during the preceding BA2 

(tailings-disposal) interval, but is about 3.6 times the background rate. 
31 

Figure 22. Summary plot showing sediment-deposition rates for sediments of BG (background), BA2 (tailings-release), BA1 (post-tailingsrelease), and AA (baseline) intervals 

Lead in Baseline versus Early Post-Tailings-Release Sediments 

Table 12 compares lead concentrations in sediments of the baseline interval (PbAA) with those in sediments of the 

early post-tailings-release interval at 13 sites. Baseline lead concentrations at these sites have a mean of 3400 +/- 1500 ppm Pb, 

and a median of 3300 ppm Pb. The area-weighted average of medians of PbAA for sites in all depositional settings is 2500 ppm 

Pb (table 12). By comparison, lead concentrations in sediments of the early post-tailings-release subinterval (PbBA1) at these 

sites have a mean of 4000 +/- 1500 ppm Pb, and a median of 4000 ppm Pb. The area-weighted average of medians of PbBA1 

for all depositional settings is 3800 ppm Pb. A Student’s t-test indicates a 69-percent probability that the populations 

represented by these two small data sets differ significantly (table 12). 

Box-and-whisker plots for the two data sets show that for the floodplain as a whole, baseline PbAA decreased relative 

to PbBA1 at the maximum, 90th, 75th, 50th, 25th, and 10th-percentile levels (figure 23). Furthermore, the area-weighted average of 

medians of PbAA/PbBA1 ratios for the floodplain as a whole is 0.83, which suggests an overall 17-percent decrease in PbAA 

relative to PbBA1 (table 12). 

The mean and standard deviation of PbAA/PbBA1 ratios is 0.87 +/- 0.28, which indicates a 13-percent decrease from 

PbBA1 to PbAA, but with a 28-percent spread at one standard deviation (table 13). While PbAA/PbBA1 ratios for levee upland 

settings decreased by about 16 to 30 percent, PbAA was unchanged relative to PbBA1 in limnetic settings, and PbAA increased 

by 14 to 18 percent relative to PbBA1 on riverbanks (as represented by three sites). 

Table 12. Lead Concentrations in Sediments of Paired Baseline and Early Post-Tailings-Release Intervals (PbAA and PbBA1) 

Figure 23.. Box-and-whisker plots, comparing interval-weighted average lead (ppm Pb) in sediments of the early post-tailings-release (BA1) 

and baseline (AA) intervals 

Table 13. Lead-Concentration Ratios of Paired Baseline- and Early Post-Tailings-Release Intervals (PbAA / PbBA1) 

Lead in Tailings-Release Sediments (PbBA2) 

Sediments of the tailings-release (BA2) subinterval probably were deposited between about 1903 +/- 8 y and about 

1968. If it took about 7.7-decades for deposition of BA-interval sediments, and 1.2-decades for deposition of BA2-subinterval 

sediments, the thickness-weighted average of lead concentrations in sediments of the BA2 interval can be approximated 

according to the equation: 

PbBA2 = (PbBA*7.7 decades) – (PbBA1*1.2 decades) / 6.5 decades. 

Substituting summary statistics for PbBA and PbBA1 into this equation yields the following estimated summary 

statistics for lead concentrations in sediments of the BA2 subinterval: PbBA2 ranges from 570 to 15,000 ppm Pb, with a mean 

and standard deviation of 6300 +/- 3500 ppm Pb, a geometric mean of 5100 ppm Pb, and a median of 5800 ppm Pb. The areaweighted average of medians for all depositional settings is 6400 ppm Pb. 

Lead in Sediments Deposited through Time 

In sediments deposited before 1886, when large-scale mining began in the Coeur d’Alene mining region, the mean of 

background lead concentrations is 31 +/- 19 ppm, and the median is 26 ppm. Metal-enriched sediments may have begun to be 

deposited on the floodplain of the main stem of the Coeur d’Alene River during the floods of 1893 and 1894. Lead-rich 

sediments of the BA2 subinterval probably were deposited between about 1903 and 1968, and the mean and standard deviation 

of thickness-weighted lead concentration in sediments of the BA2 interval is 6300 +/- 3500 ppm, with a median of 5800 ppm. 

The BA2 (tailings-release) subinterval includes basal sediments of the jig-tailings-release subinterval, and overlying sediments 

of the flotation-tailings-release subinterval (figure 24). 

Lead concentrations in sediments deposited on the floodplain of the main stem of the Coeur d’Alene River probably 

peaked during the jig-tailings-release sub-subinterval (BA2J, 1903 +/- 8y to 1918 +/- 5y). Jigs achieved poor recovery of ore 

minerals, and both coarse and slime fractions of very metal-rich tailings were discarded into streams. Lead production in the 

Coeur d’Alene region peaked in about 1917, in response to World War I. Concentrations of lead in sediment deposited on the 

floodplain may also have peaked in about 1917, when a flood washed-out tailings dams at Canyon Creek and Osburn Flats, 

transporting much of the accumulated tailings down-valley. During the BAJ sub-subinterval, lead concentrations in sediments 

deposited in Killarney Lake reached 37,000 ppm (Bender, 1991). 
32 

Figure 24 . Summary plot of lead concentrations (ppm Pb) in sediments of the background (BG) , BAJ (jig), BA2 (tailings-release), BA1 (early 

post-tailings-release) and AA (baseline) intervals. 

Flotation milling achieved improved metal recoveries, so lead concentrations of tailings decreased during the flotation 

sub-subinterval (BA2F, 1918 +/- 5 to 1968). A major flood in 1933 brought a large pulse of sediment to the floodplain. After 

the 1933 flood, sands were dredged from the river at Cataldo Landing every summer until 1967. Production of ore (and 

probably of tailings) peaked in the late 1940s, and then declined. Beginning in the early 1950s, the sand fraction of tailings was 

increasingly used as underground backfill, and only the fine fraction was discarded into streams. Thus, the amounts and grainsizes of tailings released to streams probably decreased during the late 1950s and early1960s. Finally, disposal of tailings to

streams ended in 1968. 

The mean concentration of lead in sediments of the post-tailings-release interval, deposited between 1968 and 1980, 

and sampled at 13 sites is 4000 +/- 1500 ppm, and the median is 4000 ppm. By comparison, the mean lead concentration of 

baseline-interval sediments, deposited from 1980 to about 1993 at the same sites is 3400 +/- 1500 ppm Pb, and the median is 

3300 ppm Pb. Although the mean of lead concentrations in baseline-interval sediments is 15 percent lower than that for early 

post-tailings-release sediments, the standard deviations of the two relatively small datasets overlap, and a Student’s t-test 

indicates that there is just a 69-percent probability that the populations represented by these two small data sets are statistically 

different. 

The median of lead concentrations in sediments of the baseline interval (2900 ppm Pb) is 46 percent less than the 

median of lead concentrations in sediments of the historic interval (5400 ppm Pb), and the populations are significantly 

different. However, the 2900-ppm-Pb median of baseline PbAA is nearly 1.5 times the 2000-ppm-Pb USEPA threshold for 

early remedial action on public-use sites (USEPA, 1999), 1.6 times the 1800 ppm Pb shown to cause waterfowl deaths (Beyer 

and others, 2000), and 2.9 times the 1000-ppm-Pb threshold for removal and replacement of residential yards in the Bunker Hill 

Superfund site (Richard Martindale, written communication, 1999). Furthermore, the median of baseline PbAA is 5.5 times the 

530-ppm-Pb threshold for onset of apparent effects to humans (USEPA, 1997), and 6.4 times the 450-ppm-Pb threshold for 

onset of health effects in waterfowl (Beyer and others, 2000). Also, the 2900-ppm-Pb median of PbAA is about 111 times the 

26-ppm-Pb median of background lead concentrations in sediments deposited on the floodplain of the main stem of the Coeur 

d’Alene River valley before mining began in the Coeur d’Alene mining region. 

Tonnage-Accumulation Rates for Sediments and Lead 

Table 14 shows how we calculated rates of accumulation of sediments and of lead in sediments deposited in 5 

depositional settings on the floodplain of the main stem of the Coeur d’Alene River during the background (BG), historic (BA) 

and baseline (AA) intervals, as summarized below. 

Table 14. Estimated Amounts of Lead-Rich Sediments, and Tonnages of Lead Deposited per Decade during Baseline (AA), Historic (BA) and 

Background (BG) Intervals, Coeur d’Alene River Floodplain 

The area-weighted average of medians for decadal-average thickness-increases in floodplain sediments is 3.2 

cm/decade for the baseline interval, 4.3 cm/decade for the historic interval (table 8), and about 1.0 cm/decade for the preindustrial background interval. Multiplying sediment-thickness accumulation rates by the areas of depositional settings covered

by lead-rich sediments (from Bookstrom and others, 2001), indicates decadal average rates of sediment-volume increase during 

each interval. We calculate the rate of increase in the volume of sediments as 1.72 Mm3

/10y during the baseline interval, 2.20 

Mm3

/10y during the historic interval, and 0.53 Mm3/10y during the pre-industrial background interval. Multiplying rates of 

sediment-volume increase by medians of densities of sediments (from Balistrieri and others, 2000) indicates decadal average 

rates of sediment tonnage added to the part of the floodplain covered by sediments during each interval. We calculate the rate of 

increase in the tonnage of sediments as 1.94 Mt/10y during the baseline interval, 2.49 Mt/10y during the historic interval, and

0.6 Mt/10y during the pre-industrial background interval. Multiplying rates of sediment-tonnage increase by medians of lead 

concentrations indicates tonnages of lead deposited on the floodplain per decade. 

Thus, we estimate rates of increase in the tonnage of lead on the floodplain as 5000 t Pb/10y during the baseline 

interval, as compared to 16,000 t Pb/10y during the historic floodplain-contamination interval, and 16 t Pb/10y during the preindustrial background interval. The baseline rate of lead deposition is therefore about 31 percent of the historic rate, which 

indicates that rates of lead deposition have decreased significantly since the historic interval. However, the baseline rate of

deposition of lead on the floodplain is still about 310 times the pre-industrial rate. 

Total Tonnage of Lead in Floodplain Sediments 

Multiplying median-based estimates of decadal lead-deposition rates by decades of deposition of sediments, we 

estimate that about 117 kt of lead were deposited on the floodplain from about 1903 to 1993 (table 15). This is between the 

minimum median-based estimate of 79 +/- 24 kt Pb, and the maximum mean-based estimate of 131 +/- 39 kt Pb by Bookstrom 

and others (2001), who estimated an analytical uncertainty range of +/- 30 percent. Rounding our current estimate to two 

significant figures, and applying a 30-percent range of uncertainty, our current estimate, based on medians of rates of lead 
33 

deposition during the baseline and historic intervals is 120 +/- 40 kt Pb on the floodplain of the main stem of the Coeur d’Alene 

River (table 15). This is higher than the previous median-based estimate, because it is based only on full or nearly full sections 

of sediments, whereas Bookstrom and others (2001) included both full and partial sections in order to increase representation of 

sparsely sampled areas. Nevertheless, the uncertainty range of the present estimate overlaps with the uncertainty ranges of the

previous median- and mean-based estimates by Bookstrom and others (2001). 

Table 15. Estimated Tonnage of Lead in Sediments on the Floor of the Coeur d’Alene River Valley in about 1993 

In table 15, we add our current depositional rate-based estimate of 120 +/- 40 kt Pb in sediments on the floodplain to 

previous median-based estimates of 129 +/- 39 kt Pb in the river channel, and 44 +/- 13 kt Pb in dredge spoils. Rounded to two 

significant figures, this yields a new median-based estimate of 290 +/- 90 kt Pb on the valley floor of the main stem of the 

Coeur d’Alene River valley. This median-rate-based estimate of 290 +/- 90 kt is between the median-based estimate (252 +/- 76 

kt Pb) and the mean-based estimate (320 +/- 96 kt Pb) on the valley floor by Bookstrom and others (2001). Our median-ratebased estimate is 15 percent higher than our previous median-based estimate, probably because it is based entirely on full 

sections of lead-rich sediments, and excludes data from partial sections that were included in the previous data set to improve

sample-site spacing. 

Sources and Transport of Lead-Rich Sediments 

Tailings from mills in the Coeur d’Alene mining area were the dominant primary source of lead-rich sediment in the 

drainage basin of the Coeur d’Alene River. Until 1968, mill tailings were discarded directly into tributary streams, where they

mixed with other sediment in transport. The mixed lead-rich sediment was transported downstream, and deposited down-valley 

to form secondary sources of lead-rich sediment, which are variously vulnerable to mobilization and transport. 

Secondary Sources of Lead-Rich Sediments Deposited on the Floodplain 

Box and others (in press) used the geochemical character of sediments transported and deposited by a series of floods 

between 1995 and 1997 to identify the sources of those sediments. They concluded that sediment deposited on the riverbanks 

and levees close to the river’s edge is derived from riverbed sediment remobilized from channel immediately upstream of the 

depositional site. The finer sediment deposited on the floodplain farther from the river during flood events is mobilized from a 

more complex combination of sources, including all upstream streambed sediments and, in higher energy flood events, the 

surface of the thinly vegetated portions of the floodplain (Box and others, in press). 

Although lead-rich sediments have recently been removed from large portions of some floodplains in the South Fork 

drainage basin, other portions of some floodplains remain covered with lead-rich sediments, and alluvial deposits in stream 

channels still contain fine-grained interstitial sediments that are lead-rich. During floods, such fine-grained sediments may be 

mobilized, but after floods, they settle between cobbles and pebbles in the stream bed, and are winnowed away from gravel at 

the streambed surface. 

As measured between 1994 and 1997, the average thickness of lead-rich sediments in the channel of the lower Coeur 

d’Alene River was 3.6 m between Cataldo Landing and Rose Lake, 2.6 m between Rose Lake and Cave Lake, and 1.8 m 

between Cave Lake and Harrison. These thick deposits of lead-rich sediment were deposited mostly during the 75-y time 

interval between the major flood of 1893 (shortly after large-scale milling began) and the cessation of tailings disposal in 1968 

(See Time-Stratigraphic Markers, this paper). Thus, time-averaged rates of deposition were about 48 cm/decade for deposits 

between Cataldo Landing and Rose Lake, 35 cm/decade for deposits between Rose Lake and Cave Lake, and 24 cm/decade for 

deposits between Cave Lake and Harrison. These were very high rates of sediment deposition, as compared to the probable preindustrial background rate of about 1 cm/decade (See Background Sediment-Deposition Rates, this paper). 

Bookstrom and others (2001) calculated averages of lead concentration in riverbed sediments as 2400 ppm Pb in the 

sand bar at Cataldo Landing, nearly 10,000 ppm Pb in the Dudley Reach (from the toe of the sandbar at Cataldo Landing to the 

Rose Lake bridge), 5700 and 10,000 ppm Pb for two reaches of the middle valley, and 7100 and 7400 ppm Pb for two reaches 

of the lower valley. According to their median-based estimates, secondary sources of lead-rich sediments in the channel of the 

main stem of the Coeur d’Alene River contain about 129 +/- 39 kt Pb, and riverbank sediments, previously deposited along the 

upper and outer margins of the channel at flood stage, contain about 9 +/- 3 kt Pb. These secondary sources continue to supply 

lead-rich sediment to be transported down-valley and onto the floodplain of the main stem of the Coeur d’Alene River during 

frequent floods. 

Transport and Deposition of Lead-Rich Sediment 

Fluvial processes act on secondary sources of lead-rich sediments in the river channel to mobilize, transport, and 

redeposit them along down-valley floodwater flow paths. Lead has minimal chemical mobility in natural surface waters, and is 

therefore closely associated with particles. Therefore, physical transport of lead-bearing particles by moving water is the 

predominant mode of transport for lead in the Coeur d’Alene River valley. 
34 

Physical Transport of Lead-Bearing Particles 

On the basis of periodic measurements at 21 stream gages from Mullan to Long Lake, during the water years 1999-

2001, Clark (2003, p. 35) concluded that “In contrast to cadmium and zinc, lead was transported in streams primarily in the 

particulate form, and total lead concentration at all stations was positively correlated with stream discharge. Transport of lead 

occurs primarily during elevated stream discharge when lead-rich sediments stored in stream channels and the flood plain of the

CDR [Coeur d’Alene River] are eroded and transported downstream.” Depending on flow velocity and grain size, density, and 

shape, lead-bearing particles are mobilized and transported in washload, suspended bed-material load, or bedload. 

Washload consists of clay, silt and very fine sand (less than 0.0625 mm), sufficiently fine-grained that only low 

velocity and minor turbulence keep it in suspension (Gordon and others, 1992). Washload is distributed more-or-less evenly 

throughout the water column, and it travels at the same speed as the water. Streams have very high capacity to transport 

washload, so the amount of washload carried depends largely on the rate of mobilization. When tailings were being discarded 

directly into tributary streams, the supply of mobile fine-grained sediments in washload was high year-round. Since 1968 the 

supply of washload has varied with flow, because very fine-grained sediments in pre-mine sediments along the margins of the 

main stem are cohesive, and riverbank deposits of sediments are cemented by iron oxides. Nevertheless, very fine-grained 

particles in loosely packed active riverbed sediment are mobilized at relatively sluggish flow velocities. Once in suspension, 

particles in washload suspension do not settle until flow velocity and turbulence approach zero, and then they settle gradually. 

Bed-material load consists of particles in motion that have about the same size range as particles in the streambed. 

Suspended bed material load is the portion of the bed material that is transported in suspension in the lower part of the water 

column. It is supported by the water and kept aloft by turbulence, but will settle quickly when flow velocity drops. Bedload is 

the portion of bed material that moves by rolling, sliding, or hopping, and is partly supported by the streambed (Gordon and 

others, 1992). Sizes and weights of particles transported as suspended bed-material load and bedload vary with flow velocity 

and turbulence, which vary both temporally and spatially. 

According to Leopold (1997, p. 62-63) “Bedload movement begins at discharges just less than bankfull and the bulk of 

bedload movement occurs at flows ranging from 90 percent of bankfull to twice bankfull discharge.” Lead-rich sediments that 

were previously deposited and stored within and along the river channel are vulnerable to transport during episodes of nearly 

bankfull or greater discharge. As a result, the river transports large amounts of sediment, and delivers voluminous plumes of 

suspended sediment to Coeur d’Alene Lake during episodes of bankfull or greater discharge. 

When the river overflows onto its floodplain, it transports sediment onto the floodplain in washload suspension 

throughout the water column, in bed-material suspension in the lower part of the water column, and in bed-load at the base of 

the water column. As flow velocity decreases with increasing distance from the river, sand is deposited from bedload, fine sand

and silt are deposited from suspended bed material load, and silty mud is deposited from washload. Most of the sand is 

deposited along the bed and banks of the river, but some is deposited on sand splays and distributary deltas. Fine sand and silt 

are deposited from bed-material load. As flow slackens, fine silt- and clay-sized particles settle gradually from washload, first 

in flood basins, and then throughout the floodplain and the riverbed. 

Since grain-size and weight determine settling velocity in water, and weight is a function of grain size and density, 

grains of similar size but different density settle at different rates. Lead is a heavy metal (atomic wt 207), so minerals containing 

high concentrations of lead generally have higher densities than most rock-forming minerals in alluvial sediments. For 

example, the densities of detrital grains of common lead-bearing minerals are about 7.6 for galena (lead sulfide), 6.5 for 

cerussite (lead carbonate), and 6.3 for anglesite (lead sulfate), as compared to 2.65 for quartz, 2.6 to 2.8 for feldspars, and 2.0 to 

2.7 for clay minerals (Berry and Mason, 1959). Thus, detrital grains of minerals tend to settle much faster, to be deposited much 

earlier, and to be transported much less far than similar-sized grains of common rock-forming minerals. 

Density contrasts are less between grains of rock-forming minerals, and grains of those minerals that are coated or 

partly coated by lead-bearing hydrous iron- or manganese-oxides. The density of goethite (HFeO2

) is 3.3 to 3.5, and that of 

pyrolusite (MnO2

) varies from 2.8 to 4.4, depending on whether the material is powdery or crystalline (Berry and Mason, 1959). 

Lead ions adsorbed to such oxides would increase the density of the grain coating, but the effect of lead-bearing metallic-oxide 

coatings on settling velocities probably depends mostly on the abundance of metallic-oxide coating relative to that of the rockforming mineral in the settling grain. 

Nevertheless, preferential settling of relatively dense mineral particles probably contributes to development of the 

pattern of decreasing maximum lead concentrations in floodplain sediments of the baseline interval as a function of increasing 

distance from the river (figure 14). Dilution of sediment by mixing with sediment delivered to the floodplain by lateral 

tributaries probably also contributes to development of that pattern. 

During the falling limb of each flood, flow velocity decreases, and water levels subside. Very fine-grained sediment, 

transported in washload, settles gradually onto coarser-grained sediment, deposited earlier in the flood cycle. The last sediment 

deposited is a thin layer of very fine-grained mud that settles from suspension as the floodwater recedes. Where it dries this 

mud turns to dust, which may the blown away, or washed downward through duff by spring and summer rains. 
35 

Transporting, Dispersing, and Depositing Subsystems 

Lead-bearing sediments, mobilized from mining wastes in the Coeur d’Alene mining district, are transported to the 

main stem, where large secondary sources of sediment, previously deposited along the bed and banks of the main-stem channel, 

are vulnerable to mobilization and down-valley transport during high discharge episodes. When discharge increases on the 

rising limb of a major flood, the main stem acts primarily as a transporting subsystem, which tends to erode where flow 

velocities are relatively high, and to deposit where flow velocities are relatively low. As the level of Coeur d’Alene Lake rises, 

the lower valley becomes back-flooded, and the flooded delta plain becomes a predominantly dispersing subsystem, in which 

coarse sediment is deposited on levees and deltas, and fine sediment is dispersed into lateral flood basins, and Coeur d’Alene 

Lake. During the falling limb of a flood, the river becomes a depositing subsystem. Active riverbed sediment stops moving, 

suspended sediment settles, and the riverbed returns approximately to its pre-flood configuration. As floodwaters recede from 

the floodplain, very fine-grained sediments settle from washload suspension, coating submerged surfaces with mud. 

Seasonal Cycle of Discharge and Sediment Transport 

Kjelstrom and others (1994) graphed the minimum, median, and maximum of daily mean discharge for 57 years of 

record at the Cataldo gage. Medians of daily discharges are lowest from August through October (at about 300 ft3

/s), and peak 

in April and May (at between 8000 and 9000 ft3

/s). July and August are the driest months over most of the Pacific Northwest. 

Although median flow is lowest from August through October, occasional thunderstorms may cause brief spikes in maximum 

daily discharge at Cataldo by about 500 to 1000 ft3

/s (Kjelstrom and others, 1994). 

During most of the summer, downstream flow velocity west of Cataldo Landing is nearly imperceptible, because the 

Post Falls dam holds the water level of Coeur d’Alene Lake reservoir at about the elevation of Cataldo Landing from about late 

June to late September. As a result, there is almost no downstream flow velocity and almost no downstream transport of 

sediments west of Cataldo Landing during most of the summer. Nevertheless, riverbank deposits of iron-oxide-cemented 

sediments are commonly subjected to erosion by motorboat wakes and wind-driven waves. Where and when that occurs, 

sediment from riverbanks is suspended in river water, to form reddish clouds turbid water. Because of its suspended sediment 

content, this turbid water has higher density than clear water, so it flows down the side-slope of the river channel. As the turbid 

water moves down-slope, its suspended sediment settles onto the riverbed en route to and along the deep axis of the river 

channel. This process is repeated wherever and whenever a wave hits a riverbank deposit of sediment (or a dislodged block of 

such sediment, lying at the foot of the riverbank) with enough force to mobilize sediment. Little downstream transport of such 

sediment occurs, however, until the beginning of the next episode of rising discharge and increasing downstream flow velocity. 

During autumn the water level in Coeur d’Alene Lake and the main stem of the river west of Cataldo Landing is 

lowered gradually by as much as about 2 m. Median daily discharge remains low until about mid-November, and then begins to 

increase. Return-flow of surface water and groundwater from the floodplain to the river transports dissolved metal, including 

minor dissolved lead, to the river. As mildly acidic groundwater mixes with neutral river water, reddish metal-enriched bioslime flocculates, and collects locally at the top of the zone of active bed sediment (Balistrieri and others, 2003). This watery 

floc is the most mobile bed sediment, and is mobilized by very weak currents at the beginning of the next discharge episode. 

Then bank-derived sediment, deposited on the river-bottom surface during the previous summer, probably is swept down-river 

and into Coeur d’Alene Lake before the river reaches bank-full flow. 

From late November to February, precipitation is frequent and widespread throughout much of the Pacific Northwest. 

Median flow rises to about 1000 ft3

/s during November, and then rises gradually to about 2000 ft3/s by mid-February. During 

most winters, ice forms, snow accumulates, and temperatures remain cold enough to prevent major discharges of liquid water 

until the annual spring snowmelt runoff begins. However, warm, moist southwest “Pineapple-Express” winds from the Pacific 

Ocean occasionally bring a winter thaw, accompanied by a major rain-on-snow storm. This can cause daily maximum discharge 

to peak rapidly at discharge rates up to 79,000 ft3

/s at Cataldo (Kjelstrom and others, 1994), resulting in high flow velocities, 

bank erosion, channel scour, high sediment loading, and extensive flooding. Winter floods of this type are particularly erosive, 

because they begin suddenly, when the water level in Coeur d’Alene Lake is at is low, and hydraulic head is high. The winter 

flood of 1996 had a peak discharge of 70,800 ft3

/s at Cataldo (Beckwith and others, 1996) and flow velocities in the ranged up 

to 7 ft/s at Rose Lake and Harrison (R.L. Backsen, written commun., 2002). Most of the lead was transported in association 

with suspended sediment, and only about 3 percent of the transported lead was “dissolved” in water (Beckwith and others, 

1996). 

Annual spring snowmelt runoff begins in mid-March, and peaks in April and May (Kjelstrom and others, 1994). 

During most annual spring snow-melt runoff episodes discharge increases gradually. After peaking one or more times, 

discharge then decreases gradually. A secondary peak in precipitation during May and June may increase and prolong spring 

runoff (Jackson, 1993). The entire episode tends to be relatively prolonged, and may continue intermittently from about early 

April to mid-June. While waters of upper tributary streams may be relatively clear during spring runoff, the main stem 

generally becomes turbid, though flow velocities are relatively sluggish (about 1 to 3 ft/s). Nevertheless, nearly bank-full flow 

may continue for weeks. As high discharge continues, Coeur d’Alene Lake levels rise, because the St. Joe and Coeur d’Alene 

Rivers deliver water to the lake faster than it can leave by way of the Spokane River. As the lake level rises, the western part of 

the Coeur d’Alene River valley is flooded relatively passively by water that backs up-valley from Coeur d’Alene Lake. 
36 

Although this can be considered to be lake water, it nevertheless contains suspended sediment, transported to the lake by the 

river. 

Spring and summer thunderstorms occur locally in the drainage basin of the Coeur d’Alene River, and they can cause 

local episodes of high runoff, local mass wasting, erosion, transport, and deposition, especially in hilly areas of the upper 

drainage basin, and most especially in areas where vegetation is sparse as a result of past smelter fallout, abandoned tailings

impoundments, recent logging, or cuts and fills for roads. 

Active versus Stored Riverbed Sediment 

The upper meter or so of riverbed sediment at our Dudley drill transect is sandy, poorly layered lead-rich sediment 

containing about 3000 to 4000 ppm Pb. This overlies a thicker section of well-layered sediments, in which lead concentrations 

increase down-section, from about 12,000 ppm Pb near the top, to about 27,000 ppm Pb at the base of the section of lead-rich 

sediments (figure 8). We interpret the upper layer of sandy, poorly layered sediment as active bed sediment, which has been 

recently mobilized, transported, and re-deposited. We interpret the underlying section of layered lead-rich sediment as stored 

riverbed sediment, which has not been mobilized since it was deposited in the river channel during the tailings-release timestratigraphic interval. The upper layer of active bed sediment probably forms by mixing of contaminated sediment from 

upstream and underlying secondary sources of lead-rich sediment, and uncontaminated sediment from the North Fork and 

lateral tributaries outside the Coeur d’Alene mining area. 

On the riverbed between Cataldo Landing and Rose Lake, sand dunes with amplitudes of about 0.5 to 1 m are common 

in the sandy layer of active lead-rich bed sediment. Down-river from Rose Lake, the zone of active bed sediment is less distinct 

from the underlying section of previously deposited sediments stored in the river channel. Nevertheless, grain-size generally 

decreases and lead concentrations generally increase down-section. At our Killarney drill transect, we drilled a line of holes 

across a point-bar deposit east of Strobl Marsh (figure 4). At the toe of the point-bar deposit, we drilled through a wedge of 

sandy, non-layered sediment, containing about 3000 to 4000 ppm Pb, overlying interlayered sand and silt, with lead 

concentrations increasing down-section from 4000 to 10,000 ppm Pb. The wedge of sandy active sediment thinned upslope, 

from 3 m thick at the thalweg to zero at about 50 m up the slope of the point bar (figure 6). We interpreted this wedge-shaped 

deposit of non-layered sandy sediment as active bed sediment. A ground-penetrating-radar survey by Campbell and others 

(1997) indicated contorted bedding in the layered point-bar sediments, upslope from wedge of active sediment at the toe of the 

point bar (figure 6). We interpreted this contorted bedding to indicate that layered sediments had slumped toward the toe of the 

point bar, thus moving layered sediments laterally into the zone of scour. This probably occurred in response to removal of 

lateral support, caused by scour at the toe of the point bar during episodes of high flow velocity. As flow-velocity decreases at 

the end of any high-discharge episode, active bed sediment refills the scour zone at the toe of the point bar (figure 6). 

Lead concentrations in active riverbed sediment result from a dynamic balance between processes that tend to decrease 

lead concentrations in active bed sediment versus processes that tend to increase them. Relatively sluggish currents typical of

annual spring floods may winnow fines from active bed sediment, thereby removing lead from active bed sediment, moving it 

downstream, and reducing lead concentrations in the remaining bed sediment. However, low-velocity flows probably do not 

mobilize much sediment from layered deposits, stored beneath the zone of active bed sediment. Furthermore, lead-rich fines 

probably are replenished, as flow slackens, and lead-bearing washload settles from suspension. 

During sudden-onset winter floods, fast-flowing water locally sweeps away active bed sediment, and erodes into 

underlying layered deposits of sediment, stored in the river channel. In general, the deeper such scour, the higher the 

concentration of lead in sediments mobilized from the section of stored sediments. Mobilization of sediment from these highergrade deposits tends to increase the concentration of lead in suspended sediment, as well as in moving bedload, which is 

deposited during the falling limb of the high-discharge episode, to form a new blanket of active bed sediment. 

According to measurements by Beckwith (1996) concentrations of lead in unfiltered floodwater, sampled during the 

1996 flood, increased downstream from 840 μg Pb/L Cataldo, to 4500 μg Pb/L at Rose Lake. This five-fold increase in the 

concentration of lead in transport indicates that floodwater mobilized major amounts of lead from secondary sources containing 

very lead-rich sediments that were previously deposited along the river channel between Cataldo and Rose Lake. Downstream 

from Rose Lake, the concentration of lead in unfiltered floodwater, sampled during the 1996 flood increased by a factor of 1.4,

from 4500 μg Pb/L at Rose Lake to 6500 μg Pb/L at Harrison. 

Down-Cutting versus Aggradation in the River Channel 

In general, scour occurs during the rising limb of a major flood, and deposition occurs during the falling limb. At the 

end of the flood, scour and fill roughly balance if the river-channel profile is in dynamic equilibrium. Over the long term, 

however, the Coeur d’Alene River has aggraded, filling the bedrock valley with 60 to 130 m of unconsolidated sediments since 

the Pleistocene (Norbeck, 1974, and U.S. Army Corps of Engineers, 1952). During the historic interval of mining and release of 

mill tailings to tributary streams, the rate of aggradation was unnaturally high, as an average of nearly 3 m of lead-rich 

sediments was deposited in the river channel (Bookstrom and others, 2001). Now that tailings are no longer being discarded 

into streams, it is not known whether the river channel will restore long-term equilibrium by degrading toward its pre-mining 
37 

profile, and thereby mobilizing increasingly lead-rich sediments down-section, or by aggrading, and thereby covering stored 

lead-rich sediments with a thickening blanket of post-tailings sediment. 

When the dredge operated at Cataldo Landing, excavation of the dredge pond created a trap for sandy sediment, which 

the dredge removed annually, and deposited on the floodplain at Cataldo Flats. As the upper end of the trap filled, its lower end 

was eroded, until a new equilibrium was approached. Depth profiles for the years 1930, 1940 and 1950, measured at a location 

1.5 mi downstream from the Cataldo dredge pond indicate that maximum river depth increased by a factor of 1.5, and river 

width increased by a factor of 1.15 during the time interval from 1930 to 1950, when the dredge was active (Grant, 1952). After

the dredge was dismantled in 1968, the dredge pond filled with about 4.5 m of sand containing about 2000 ppm Pb from bottom 

to top of the section (USEPA, 1998). At our Dudley transect, the 1 m layer of active sand, which overlies layered tailings-rich

sediments, probably has formed since the dredge stopped removing medium-grained sand, allowing much more of it to be 

carried on down the river. Thus, from Cataldo Landing to Dudley, the river probably has undergone net aggradation since 

dredging at Cataldo Landing stopped. 

During the 1996 winter flood, USGS Water Resources personnel measured depth profiles across the river at the Rose 

Lake Bridge. These profiles indicate on the southern margin of the thalweg, 1.5 m of deposition was followed by 3 m of scour. 

Meanwhile, on the northern margin of the thalweg, sediment accumulated throughout the flood, to a total thickness of up to 3 m 

(R.L. Backsen, unpub. data, 1996). After the flood, there was a small net gain in the overall elevation of the river bottom across 

the Rose Lake transect. By contrast, small net losses were recorded at the Cataldo and Harrison gages. 

After the 1996 flood we observed and photographed several locations between Cataldo Landing and Rose Lake where 

well-layered deposits of sediments had been scoured, so that fresh, steeply eroded exposures of well-layered sediments were 

visible under water, especially near the margins of the river channel. At the site of our Dudley drill transect a log, which had 

previously been buried in laminated lead-rich sediments, extended at least 2 m into open water after the flood. Thus, lead-rich

sediments, historically deposited in the river channel, continue to be eroded locally during episodes of high discharge and high 

flow velocity, even though minor net deposition may be recorded at the end of the high-discharge episode. 

Deposition and Storage of Lead-Rich Sediment on the Floodplain 

When the river overflows its channel, floodwater carries lead-bearing sediment onto the floodplain. That sediment is 

deposited progressively as floodwater spreads and loses velocity. Levee-sand plumes commonly extend down-valley from the 

lower outside margins of river-meander bends. This pattern indicates that when the river overflows from meanders, the 

overflow is directed more-or-less straight down-valley, progressively depositing sand as it moves away from the river, spreads

onto the floodplain, and loses velocity. As relatively coarse sediment from the river channel is deposited on levees, currents 

outside the channel probably winnow fine-grained oxidation products from levee sands, and transport them into flood basins. 

In reducing environments of marshes and lakes, metallic oxy-hydrides, transported from oxidizing environments on 

levee uplands, are reduced. Reduction breaks down metallic oxy-hydrides and releases metallic ions, which combine with 

sulfide ions (produced by sulfate-reducing bacteria) to form authigenic sulfidic-metallic materials that are non-stoichiometric

and amorphous to nano-crystalline (Thornburg and Hooper, 2001). These materials have enormous surface area, and are much 

more chemically reactive than detrital grains of crystalline metallic sulfide minerals. The lead in these authigenic sulfides is 

therefore much more bio-reactive and bio-available than the lead in detrital grains of galena.

Fluvial Process Rates 

Comparisons of estimated riverbank erosion rates with rates of transport of suspended sediment in the river indicate 

that riverbanks supply only a minor proportion of the lead-bearing suspended sediment that degrades the quality of water in the

river and Coeur d’Alene Lake during high-discharge episodes. Comparisons of riverbank erosion rates with rates of sedimentdeposition on the floodplain and in Coeur d’Alene Lake indicate that riverbanks supply only an incidental proportion of the 

lead-rich sediments deposited on the valley floor. 

Annual Rates of Riverbank Erosion 

Since about 1968, bank-wedge deposits of sediments have been eroding laterally, while still receiving vertical 

accumulations of sediment. Stratigraphic sections of bank-wedge deposits are thereby exposed along steep cut-banks, which 

retreat laterally, toward the levee crest (figure 6). Inasmuch as bank-wedge deposits thin toward the levee crest, progressive 

lateral erosion of cut-banks exposes progressively thinner remnants of the bank-wedge deposits, at increasingly higher levels in 

the retreating cut-banks. This is particularly obvious along relatively narrow reaches upstream from the Killarney segment 

(figure 4). There, levee crests are relatively high and close to the river, and the slope along the base of the riverbank wedge of 

sediments is relatively steep. Downstream from there, levee crests are progressively lower and farther from the river, so the 

slope at the base of the section of sediments is relatively gradual. 

Wetzel (1994) judged the severity of bank erosion by scoring for bank stability, bank condition, vegetative cover, 

bank-channel shape, and evidence of in-channel erosion, or deposition. At three sites below Cataldo Landing, she judged bank 
38 

erosion severe at two sites, and moderate at one site. She applied an empirically calibrated table to convert “severe” to an 

estimated 9 to 15 cm/y, and “moderate” to an estimated 2 to 6 cm/y of lateral bank recession. 

Using the same method, Flagor (2002) judged long-term (about 20-y average) annual rates of lateral bank-recession at 

143 selected observation-point sites along the main stem of the Coeur d’Alene River. All of these sites were along very severely 

eroded segments of riverbank, which he scored as 5.5 to 6 (on a scale of increasing severity from 0.1 to 5 +). To calibrate these 

scores, Rob Sampson surveyed a limited number of sites where fence-posts, culverts, trees or shrubs could be used to measure 

the distance of bank retreat during an estimated time interval. Applying this calibration to the rated sites, Flagor (2000) 

estimated bank retreat rates of about 7 to 8 cm/y for the 143 severely eroded sites that he examined. 

At 13 pairs of staked locations on opposite sides of the river, between Cataldo Flats and Harrison, we made a total of 

50 measurements of bank retreat rates, by measuring the horizontal distance from a stationary stake, placed a few meters back 

from the top of the riverbank to the vertical projection of the riverbank face. We did this at 34 sites for the time interval from 

1996 to 2000, and Michael Pereira and M.D. McFadden did this for eight sites for time intervals from 1996 to 2002 and 2000 to 

2002. No major winter floods occurred during the time intervals of these measurements (late 1996 to late 2002). 

The overall mean and standard deviation of bank-recession rates measured in this way was 8.9 +/- 15 cm/y, the 

minimum was 0 cm/y, the maximum was 96 cm/y, and the median was 5.1 cm/y (S.E. Box, A.A. Bookstrom, Michael Pereira, 

and M.D. McFaddan, unpublished data, 1996 to 2002). The median of bank-recession rates along the outside margins of 

meanders was 8.6 cm/y, as compared to 3.8 cm/y along relatively straight reaches, and 3.3 cm/y along inside margins of 

meanders. On the basis of these measurements, we made median- and mean-based estimates of tonnages of sediments eroded 

annually from riverbanks, as calculated in table 16. Our median-based estimate is that 6.1 kt/y of sediment is eroded from 

riverbanks, and our mean-based estimate is that 11.7 kt/y of lead-rich sediment is eroded from riverbanks (table 16). 

The overall mean of lead concentrations in riverbank-wedge deposits is about 6300 g/t (Bookstrom and others, 2001). 

Multiplying this lead concentration by estimated tonnages of lead-rich sediment removed from riverbanks yields a medianbased estimate of 38 t/y of lead, and a mean-based estimate of 74 t/y of lead removed from riverbanks by lateral erosion. The 

mean-based estimate is influenced by a few very high bank-retreat rates, at sites where large blocks collapsed onto the wave-cut 

bench at the base of the riverbank. Such blocks commonly disaggregate and erode slowly, and gradually release lead-rich 

sediment to the river for many years. The mean-based estimate is therefore influenced very high bank-retreat rates that are 

much higher than sediment-mobilization rates. By contrast, the median-based estimate of bank-retreat rates is much less 

influenced by very high bank-retreat rates, and is therefore a better indicator of sediment-mobilization rates resulting from 

lateral erosion of riverbanks. We therefore favor the median-based estimate of 38 t/y of lead released by lateral erosion of 

riverbanks. 

Table 16. Estimated Tonnage of Lead-Rich Sediment Released Annually by Riverbank Erosion, Coeur d’Alene River, West of Cataldo Landing 

Annual Rates of Deposition from Riverbank to Levee Crest 

Annualized baseline rates of deposition of lead on bank-wedge deposits (from the riverbank to levee crest) are similar 

to annual rates of lead mobilization by lateral erosion of riverbanks from 1996 to 2002, which indicates that vertical deposition 

of lead in sediments added to riverbank-wedge deposits is nearly in dynamic balance with lead mobilized by lateral erosion of 

riverbanks. The median of annualized baseline sediment-deposition rates along riverbanks is 0.64 cm/y, and the mean is 0.69 

cm/y. The average thickness of sediment deposited on the bank-wedge deposit is about 70 percent of the thickness measured at 

the bank. Therefore, a median-based estimate of the average thickness of the bank-wedge deposit is 0.0045 m/y, and a mean 

based estimate is 0.0048 m/y. The total area of bank-wedge deposits along the main stem west of Cataldo Landing is about 2.15 

x 106

 m2 (Bookstromand others, 2001). Multiplying thickness by area, a median-based estimate of the baseline volume of 

sediment deposited annually is 9630 m3

, and a mean-based estimate is 10,400 m3. We multiply these volumes by the 1.6 t/m3

dry density of bank sediment (Bookstrom and others, 2001) to estimate that 15,400 t/y to 16,600 t/y of sediment are deposited 

on riverbank wedges. Multiplying these estimated tonnages of sediment by the concentrations of lead in baseline sediments on 

riverbanks (median 3300 g/t, mean 3400 g/t) yields a median-based estimate of 51 t Pb/y and a mean-based estimate of 56 t 

Pb/y deposited on riverbank wedges during the baseline interval. The true central tendency for both populations probably is 

between the median-based and mean-based estimates. The average of median- and mean-based estimates lead-release by bank 

erosion rates 56 t Pb/y, and the average of median- and mean-based estimates of lead deposition from summer water level to the 

levee top is 54 t Pb/y. 

Annual Rates of Sediment Transport in the Coeur d’Alene River 

Woods (2001) reported discharge and concentration of suspended sediments transported by the river, as measured at 

the Rose Lake and Harrison gages during March, June, September, and October of 1999. Clark and Woods (2001) graphed 

relationships between discharge and concentration of suspended-sediment and bedload-sediment discharge for the time period, 
39 

between February of 1999 and April of 2000. At the Rose Lake and Harrison gages the suspended-sediment load was primarily 

composed of fine-grained sediment, and bedload transport was either negligible or nonexistent on most of the sampling dates, 

which all had stream discharge less than 15,000 ft3

/s. 

USEPA (2001) estimated average annual sediment transport as a function of discharge for each year from 1992 to 

1999 on the basis of periodic stream discharge measurements, and the lognormal relationship between stream discharge and 

sediment discharge, as graphed by Clark and Woods (2001) for the period from February of 1999 to April of 2000 (during 

which stream discharge did not exceed 15,000 ft3

/s). 

The means and standard deviations of tonnages of suspended sediment transported annually past the Rose Lake and 

Harrison gages, as estimated by USEPA (2001) were 24 +/- 20 kt/y at the Rose Lake gage, and 73 +/- 110 kt/y at the Harrison 

gage (table 17). These could be considered as minimum estimates, because they are based on relationships between discharge 

and sediment transport that were measured at stream discharges of less than 15,000 ft3

/s, which was insufficient to activate 

bedload transport. Average annual rates of transport, estimated in this way do not adequately represent relatively short episodes 

of very high discharge, such as the 1996 winter flood.

Annual Rates of Deposition of Floodplain Sediments and Coeur d’Alene Lake Sediments 

In table 14 we estimated the decadal average rate of deposition of sediments on the floodplain for the baseline interval 

as 1.94 Mt of sediment/10y, or about 190 kt of sediment/y (as rounded to two significant figures in table 17). About 37 percent

(70 kt of sediment/y) was sandy sediment that was deposited on riverbanks, levees, and sand splays, and about 63 percent (120 

kt of sediment/y) was silty to muddy sediment that was deposited in flood basins (table 17). 

In table 2 we estimated mean baseline rates of deposition of sediments on the floor of Coeur d’Alene Lake as 11.7 

cm/10y on the toe of the Coeur d’Alene River delta, and 0.4 cm/10y on the floor of the distal lakebed. To calculate the decadal

increase in volume, we multiplied these rates of increase in thickness by the area of the delta toe and the lake bottom, 

respectively. To calculate the decadal increase in dry tonnage of sediment, we multiplied by densities of 1.4 t/m3

 of sediment for 

sandy delta sediments, and 1.07 t/m3

 of sediment for water-saturated distal lake-bottom sediments (from Bookstrom and others, 

2001). To convert decadal to annual rates, we divided by 10, and rounded to two significant figures. In table 17, the results of 

those calculations indicate that during the baseline interval, the delta toe received about 160 t of sandy to silty sediment per 

year, while the distal lake bottom received about 40 t of silty to muddy sediment per year. 

Table 17. Mean Annual Sediment-Transport Rates in the Coeur d’Alene River (1992-1999), and Baseline Sediment-Deposition Rates, Coeur 

d’Alene River Floodplain, and Coeur d’Alene Lake (1980 ~1993) 

Mobilization and Transport of Sediment along the Main Stem 

In 1993 and 1994, with mean annual stream flows between 36 and 58 m3/s, the annual lead load was about 5 times 

higher at Rose Lake than at Cataldo, and the load at Harrison was 3 to 4 times higher than at Cataldo (as calculated from the 

data of Beckwith and others, 1997). During the 1996 flood, as measured discharge decreased from 1900 m3

/s at Cataldo, to 

1430 m3

/s at Rose Lake and 1350 m3/s at Harrison, but lead load was about 4 times higher at Rose Lake than at Cataldo, and 

was about 5 times higher at Harrison than at Cataldo (as calculated from the data of Beckwith and others, 1996, and Beckwith, 

1996). These comparisons indicate that during high-discharge episodes, lead mobilization and transport increase by a factor of 4 

to 5 along the reach from Cataldo to Rose Lake. We suggest that most of that increase probably occurs downstream from 

Cataldo Landing, where the river bottom changes from cobble gravel with interstitial fines, to more-easily mobilized and 

transported sand with a higher proportion of interstitial fines. 

Nevertheless, there is much uncertainty in estimating mobilization and transport of lead from different reaches of the 

South Fork and main stem during episodes of differing discharge and duration, because most of the data are for suspended 

sediment only, and mobilization is not simply additive down-stream. For example, sediment that is mobilized in any reach is 

mixed with sediment already in transport from upstream, and some of the sediment that is transported into or mobilized within 

any reach may be re-deposited before it reaches the next gage. The amount of sediment in suspension and the lead content of 

that sediment probably vary according to flood stage, source proximity, current direction and velocity, and distance from the 

river, so sampling at different times, different locations, or by different methods can yield different results, as indicated by the 

data of Box and others (in press). 

Mobilization of Sediment from Main-Stem Riverbanks 

In table 17, we compare estimated tonnages of sediment eroded annually from riverbanks versus estimated tonnages of 

suspended sediment transported annually past the Rose Lake and Harrison river-flow gages. Our median-based estimate of the 

tonnage of sediment mobilized annually by bank erosion is about 6 kt of sediment/y, and our mean-based estimate is 12 kt of 

sediment/y. That amounts to about 8 to16 percent of the mean annual tonnage of suspended sediment transported past the 

Harrison gage. Thus, although bank erosion produces local small-scale plumes of reddish sediment at summer water level, it 

contributes only about 8 to 16 percent of the suspended lead-bearing suspended sediment that is transported past the Harrison 
40 

gage and into Coeur d’Alene Lake during high-discharge episodes, which the only time when contamination of surface water 

by suspended particles of lead-rich sediment becomes pervasive and widespread. 

Mobilization and Transport of Sediment from the Main-Stem Riverbed 

Inasmuch as lead loads increase by factors of 3 to 5 between Cataldo and Harrison during episodes of high discharge, 

we estimate that about 1/3 to 1/5 (or 20 to 33 percent) of the lead load measured at Harrison could be derived from sources 

upstream from Cataldo. If 8 to 16 percent of the lead load measured at Harrison is from riverbank erosion, then the remaining 

51 to 72 percent of the lead load measured at Harrison probably is from the main-stem riverbed. Thus, the main-stem riverbed 

is the dominant source of lead-rich sediment that is mobilized, transported in suspension, and deposited downstream from 

Cataldo. If we had data on the amount of lead transported in bedload and in bed-material load during major floods, we could 

increase these estimates of the proportion of lead-rich sediment mobilized from the main-stem riverbed. 

River Transport versus Floodplain Deposition Rates 

The total of the means of estimated tonnages of suspended sediment transported annually past the Rose Lake and 

Harrison gages accounts for only about half of our median-based estimate of the tonnage of sediment deposited annually on the 

floodplain, and only about a quarter of the total tonnage of metal-enriched sediment estimated to be deposited annually on the 

floodplain and the floor of Coeur d’Alene Lake (table 17). One reason for the apparent mismatch between the means of 

estimated annual rates of transport and deposition is the high variability of annual flow and transport, as represented by standard 

deviations that are nearly as large as, or larger than the means. Nevertheless, the mismatch between rates of transport and 

deposition may be even greater than it appears in this comparison, because transport at the Rose Lake should not be simply 

added to transport at the Harrison gage. Transport between the gages involves not just additive mobilization, but also input from 

upstream, and deposition between gages. Furthermore, transport measured at stream gages only spans only the river channel, 

which is about 100 m wide, whereas data on rates of sediment deposition span the entire floodplain, which is about 2 km wide. 

Water that leaves the river between gages eventually returns to the river, but much of the sediment that leaves the river between 

gages is deposited on the floodplain, and therefore may not be recorded at downstream gages. 

Another possible reason for the apparent mismatch between rates of sediment transport and deposition is that bedmaterial load and bedload are not sampled at high discharge. While mud and fine silt are transported in washload suspension 

throughout the water column, coarser silt is transported in bed-material load in the lower part of the water column, and sand is 

transported near the base of the water column, in bed-material load and bedload. Thus, the gages do not record sand that is 

deposited on riverbanks, levees, sand splays, lateral-lake deltas, and the delta of the Coeur d’Alene River in Coeur d’Alene 

Lake. Furthermore, the Harrison gage does not record sediment that enters Coeur d’Alene Lake from the St. Joe drainage basin, 

or from smaller tributaries to Coeur d’Alene Lake. 

Comparison of our mean-based estimates of the tonnage of sediment mobilized annually by bank erosion (about 6 to 

12 kt/y), relative to estimated annual rates of deposition of sediment on the floodplain (about 190 kt/y), indicates than bank

erosion could contribute only about 3 to 6 percent of the lead-rich sediment deposited annually on the floodplain. Similarly, 

even if all of that bank-derived sediment were transported to Coeur d’Alene Lake, we estimate that bank erosion could supply 

only about 3 to 6 percent of the 200 kt/y of metal-enriched sediment deposited on the floor of Coeur d’Alene Lake. If the bankderived sediment were divided between the floodplain and the bottom of Coeur d’Alene Lake, we estimate that bank erosion 

could supply only about 1.5 to 3 percent of the approximately 390 kt of metal-enriched sediment deposited annually on the 

floodplain and the bottom of Coeur d’Alene Lake (table 17). 

Long-Term Contamination in River Systems 

Mining-derived metal-enriched sediment that is deposited in transport-dominated river channels generally undergoes a 

long history of remobilization, dilution during transport, and re-deposition to form and re-form persistent “hot spots,” which 

continue to function as secondary sources of pollution. However, once metal-enriched sediment is deposited in predominantly 

depositional environments, such as lateral flood basins, it tends to remain, and is buried by a successively younger layers of 

progressively diluted, and less metal-enriched sediments. For riverbed sediments to become diluted to background 

concentrations, and for contaminated flood-basin sediments to be buried by uncontaminated sediments takes centuries, 

depending on the size and metal contents of secondary sources, and the size and discharge of the drainage basin they occupy. 

Modeling Studies 

Coulthard and Macklin (2003) modeled long-term contamination in river systems from historical metal mining by 

applying a sediment-catchment model that uses historical mining records to predict present-day and future levels and patterns of 

contamination. Their results indicate that contaminated sediments collect to form “hot spots,” which become secondary sources 

of pollution, and that more than 70 percent of the deposited contaminants remain within the river system for more than 200 y 

after mine closure. Thick deposits of highly contaminated sediments along the Dudley reach are a major example of such a 
41 

“hot-spot” secondary source, which (unless removed by dredging) can be expected to remain within the river for more than 200 

years after tailings ceased to be discarded directly into tributary streams. 

Stratigraphic Studies 

Leblanc and others (2000) studied the stratigraphic section of metal-enriched sediments, deposited in the 

predominantly depositional estuary of the Rio Tinto River, downstream from a massive-sulfide mining district in Spain, since 

mining began there about 4,500 years ago. Sediments derived from Copper-Age mining were buried by sediments with 

progressively lower lead concentrations, which approached the background concentration 450 y after cessation of small-scale 

Copper-Age mining. An upper interval of metal-enriched sediment extends from 1.3 m deep to the surface. Lead concentrations 

increase up-section in this interval, from 100 ppm Pb in sediments deposited during pre-Roman mining, about 3,900 years ago, 

to 5300 ppm Pb in surface sediments, still being deposited in response to present-day mining. 

Long-Term Future Contamination in the Coeur d’Alene River Valley 

Modern mining has rapidly brought massive amounts of mining waste to the surface in the drainage basin of the Coeur 

d’Alene River. Large secondary sources of sediment have formed downstream from the mines. Most of the deposited 

contaminants can be expected to remain within the Coeur d’Alene River system for more than 200 years after the 1968 

cessation of tailings disposal into streams. Unless large secondary sources of lead-rich sediments are removed or stabilized, 

they probably will continue to supply lead-enriched sediment to floodwaters for much longer than the 450 years it took for the 

Rio Tinto River and its floodplain to fully recover from small-scale releases of Copper-Age mining wastes. 

Long-Term Monitoring 

Long-term monitoring could provide answers to questions relevant to remedial design. For example, is the river in 

dynamic equilibrium with its longitudinal profile, or is it down-cutting or aggrading over the long term? An answer to this 

question would provide a basis for choosing between removal and in-situ stabilization of lead-rich riverbed sediments as the 

best way to reduce the severity of long-term contamination of the valley floor. The best way to answer this question would be to 

conduct periodic sonar mapping of the entire river channel (as was recently done by AVISTA, unpub. data, 2004). Short of that 

cross-sections of channel depth could be made periodically at key locations, either by depth sounding with a weighted cable, or

by sonar profiling. 

Are rates of riverbank erosion increasing or decreasing through time? An answer to this question could influence the 

priority given to removal of riverbank deposits of lead-rich sediments. To answer this question, periodic surveys of riverbank 

retreat could be expanded and continued long-term. At a minimum the 13 sites previously monitored for bank retreat could be 

re-visited after each high-discharge episode, and at the beginning and end of at least one representative summer season. In 

addition to measuring the retreat of bank tops, retreat of the entire bank profile could be measured. Monitoring upstream, 

downstream, and across from bank-stabilization pilot projects would test for indirect changes related to those projects. 

How and why are concentrations of lead in active bed sediments changing through time? Answers to such questions 

will promote understanding of how the composition of active bed sediments reacts to discharge episodes of different 

magnitudes and durations, and how upstream remediation may reduce lead concentrations in mixed active sediment 

downstream. Stephen Box (unpub. data, 2005) has begun such a program of periodic sampling of riverbed sediment. 

How and why are depositional rates and lead concentrations of sediment deposited on the floodplain changing over the 

long term? Answers to such questions would provide a basis for evaluating the effectiveness of remediation intended to prevent 

or lessen continuing floodplain contamination. To answer such questions, depositional rates and lead concentrations in 

sediments deposited on the floodplain could be monitored periodically over the long term. Monitoring future depositional rates 

would require placing an artificial time-stratigraphic marker, such as a semi-permeable fabric, staked in place on the sediment

surface, to collect sediment deposited during the time-stratigraphic interval to be studied. However, since the difference 

between baseline and historic depositional rates is not statistically significant, it may be sufficient to test only for changes in 

lead concentrations in surface sediments deposited over time. If sampling was done on 10-year intervals, and samples were 

taken from within the upper 8 mm of mineral-dominated sediment, most samples would include only sediment deposited within 

the 10-year sampling interval (even though most depositional rates vary from 6.9 +/-5.3 cm/10y on riverbanks to 2.5 +/- 1.7 

cm/10y in palustrine settings (table 3). Given the wide ranges of spatial variations in lead concentrations indicated by our data, 

a large number of sample sites, distributed in proportion to the areas of representative depositional settings, would be required 

to test for overall changes in lead concentrations of sediments deposited on the floodplain over time. 

Implications for Remediation 

The data presented here provide critically important information about the rates of deposition of metal-enriched 

sediment in the floodplain of the lower Coeur d’Alene River and the sources and processes that result in this distribution. In

some cases our present understanding is enough to compel us to provide a note of caution that some remediation approaches 
42 

will not result in lasting solutions. In other cases our present understanding of processes that control this continued 

redistribution is fraught with uncertainty, and we believe that further efforts at clarifying these controls should be undertaken 

before proceeding with other remediation approaches. In this section we discuss the impacts that some of the rates and 

processes of metal-enriched sediment redistribution could have on various remediation approaches. 

The most obvious implication from this study is that metal-enriched sediment continues to be deposited on the 

floodplain of the lower Coeur d’Alene River at relatively high (but variable) rates and is likely to continue to do so into the

foreseeable future. Remedial actions intended to result in soils on the surface of the floodplain with background metal 

concentrations (for example, removal of historical metal-enriched deposits to expose pre-mining soils, or capping of the surface 

with clean soil) will be undone within a few years by new deposition of metal-enriched sediments, unless preventative actions 

are taken. We note that depositional rates are highest closest to the river (6.4 cm or 2.5 inches of sediment containing 3300 ppm 

Pb per decade), such that capping or excavation of river banks or the adjacent riparian areas of the natural levees of the river are 

particularly susceptible to (and difficult to protect from) rapid recontamination. However, the depositional rates of metalenriched flood sediment, even in marshes far from the river, are high enough (averaging 2.5 cm or 1 inch of sediment with 2100 

ppm Pb per decade) to effectively re-contaminate the surface within several years. Thus, for remediation to be effective over the 

long term, the problem of post-remediation recontamination will need to be dealt with successfully in all remediation efforts on 

the floodplain. 

One way to deal with continuing contamination in relatively small but popular public-use sites would be to remediate 

repeatedly, as needed. Boat launches, parking lots, camp grounds, and picnic areas could be largely paved, so that they could be 

re-cleaned repeatedly by sweeping, or washing, or both. This would require long-term funding for monitoring and re-cleaning 

as necessary. Although practical for relatively small sites, this approach would be much less practical for extensive areas, such 

as riparian riverbanks and levees along both sides of the main stem of the Coeur d’Alene River from the confluence of the 

North and South Forks to Coeur d’Alene Lake. 

Preventing or decreasing the extent or severity of cumulative recontamination of remediated areas of the floodplain of 

the lower Coeur d’Alene River would require either (1) isolation of the remediated area from future flood waters, (2) reduction

of the metal content of future flood-borne sediment to acceptable levels, or some combination of both. Isolation of a remediated 

area of the floodplain from sediment-laden floodwater might be accomplished by raising physical barriers to encroaching 

floodwaters. Isolation would be feasible for some lateral wetlands, but probably not along riverbanks, which are within the 

margins of the high-water channel of the river. Ultimately the severity of recontamination could be decreased by reducing the 

concentrations of metals transported during future floods. Such reduction could be accomplished by changing the mixture of 

metal-rich and metal-poor source components mobilized during floods, either by reducing the relative amount of metal-rich 

component or by increasing the relative amount of metal-poor component mobilized. Reducing mobilization of the metal-rich 

component could be promoted by removing metal-rich sediment from source areas vulnerable to erosion, or by immobilizing 

such sediments in place. Dilution could be promoted by increasing mobilization of metal-poor sources relative to mobilization 

of metal-rich sources. Based on geochemical signatures, the dominant source of sediment deposited during floods in the 

riparian zone (river bank and natural levee) along the lower Coeur d’Alene River is streambed sediment re-mobilized from the 

adjacent river reach (Box and others, in press). The finer sediment deposited on the floodplain farther from the river during 

flood events is mobilized from a more complex combination of sources, including all upstream streambed sediments and, in 

higher energy flood events, the surface of the thinly vegetated portions of the floodplain (Box and others, in press). Metal-poor 

source components of this finer suspended sediment consist primarily of fine sediments derived from the North Fork of the 

Coeur d’Alene River, with lesser contributions from relatively uncontaminated tributaries upstream in the South Fork and mainstem of the Coeur d’Alene River, and from tributaries discharging directly onto the floodplain of the lower Coeur d’Alene 

River. 

Given that most of the floodplain is covered with metal-enriched soils, remediation has been suggested for areas 

ranging from riparian riverbanks, which serve as recreational areas for humans and feeding areas for song birds, to more distal

marshes that serve as recreational areas for humans and feeding areas for waterfowl. Public-use areas, such as boat launches, 

picnic sites, and the bike trail along the railroad embankment can be paved, and re-cleaned as necessary, as long as there is 

funding to pay for such care and maintenance. However, paving and re-cleaning probably would not be practical for the entire 

area of the riverbanks, which is about 2.2 km2

 (from summer water level to the levee top, on each side of the river, and from 

Cataldo Landing to the river mouth, as estimated by Bookstrom and others, 2001). Stabilizing riverbanks will prevent erosion, 

but will not stop continuing deposition of lead-rich sediments along the stabilized riverbanks. Isolation of riparian areas along 

the immediate river banks would also be impractical, because riverbanks are within the high-water channel of the river. 

Areas farther from the river could be more-or-less isolated by artificial dikes. For example, the 1889 railroad 

embankment along the south side of the Coeur d’Alene River valley provides a long-lived example of such a physical barrier, 

albeit with physical passages through the barrier at numerous bridges. Several floods have overtopped that embankment during 

its 115 year history, and many sections of that embankment have been eroded through by floodwaters (as occurred extensively 

during the 1996 flood). Although metal contents are typically lower in soils south of the railroad embankment (for example, 

Lane Marsh south), soil metal contents in these protected areas are generally still well above background values, and in many 

cases exceed levels that are considered injurious to human or wildlife health. Thus, any protective flood barrier built to protect a 

remediated wetland would need to be built higher, and to be constructed of more erosion-resistant materials than those of the 

historical railroad embankment. At distributary outlets from the main channel, some type of gate would be necessary to block 
43 

lead-bearing floodwater from entering lateral lakes and marshes fed by distributaries. One disadvantage of building such a 

barrier is that it would constrict the floodway, resulting in concentration of floodwater flow, and sediment transport and 

deposition between the river and the dike. This has occurred between the river and the railroad embankment in Lane Marsh 

north (table 5). Constraining flood waters to a narrower floodway would also increase the load of metal-enriched sediment to 

Coeur d’Alene Lake. 

Reduction of the metal content of future flood-borne sediment is a mixing problem, which could be approached by 

decreasing mobilization and transport of sediment from metal-rich sources, or increasing mobilization of metal-poor sediment 

from metal-poor sources, or both. Decreasing mobilization and transport of metal-rich sediment could be accomplished by 

removing secondary sources of metal-enriched sediments from the channel and banks of the river, or by in-situ stabilization of 

such sources, so that they would not be mobilized at likely maximum flow velocities (about 7 ft/s). Metal-poor sediment is 

being mobilized at abnormally high rates as a result of deforestation and surface disturbances caused by human activities that 

expose unconsolidated soil, colluvium, and alluvium to erosion and transport down-gradient. Additional dilution of metalenriched sediment in-transport could be achieved locally by artificially placing clean sediment at key locations along a stream, 

so that it would be mobilized, transported, and deposited onto a chosen target area by predictable currents resulting from a highdischarge episode. 

Remediation Options for Reducing Metal contents of Flood-Borne Sediment 

A number of remediation options have been suggested that are aimed at reducing the metal content of flood-borne 

sediment in the lower Coeur d’Alene River valley. Based on our present understanding of the sources of flood-borne sediment 

and the processes that mobilize it, we briefly discuss several remediation options that have been suggested. 

Source Control by Removal or Stabilization of Riverbanks 

Removal or stabilization of lead-rich riverbank deposits has been suggested as a method to reduce the lead load in 

sediment transported and deposited in the lower Coeur d’Alene River valley, Coeur d’Alene Lake, and the Spokane River. 

Erosion of riverbank deposits by the wakes of passing boats produces turbid water, transferring bank materials to deeper water. 

Most of the sediment transported in such turbidity plumes is temporarily re-deposited on the riverbed, near its site of 

mobilization from the riverbank. Oxidized lead-rich sediment eroded from riverbanks by boat wakes probably is mobilized 

during the rising limb of the next high-discharge episode. Our analysis indicates that the riverbanks supply about 8 to 16 

percent of the suspended sediment transported past the Harrison gage during high-discharge episodes, the only time when 

water-quality is widely and pervasively degraded by lead associated with suspended sediment. Lead/zinc ratios of suspended 

sediment samples collected during the floods of 1996 and 1997 are interpreted to indicate a relatively small input from eroding

riverbanks (Box and others, in press). Therefore, removal or stabilization of riverbank deposits will make only a relatively 

minor contribution to improvement water quality during high-discharge episodes, when the waters of the Coeur d’Alene River, 

Coeur d’Alene Lake, and the Spokane River often transport lead-bearing sediment in suspension. 

Source control to reduce ongoing contamination of the floodplain and the bed of Coeur d’Alene Lake is another 

purpose for removal or stabilization of deposits of lead-rich sediments on riverbanks. However, our analysis indicates that 

riverbank-erosion accounts for only about 3 to 6 percent of the annual tonnage of lead-rich sediment that is deposited on the 

floodplain, or about 3 to 6 percent of the annual tonnage of lead-rich sediment that is deposited in Coeur d’Alene Lake, or about 

1.5 to 3 percent of the combined annual tonnage of lead-rich sediment that is deposited on the floodplain and in Coeur d’Alene 

Lake (table 17, middle part). Thus, removal or stabilization of riverbank deposits of lead-rich sediment would produce only an 

incidental reduction in the amount of lead-rich sediment deposited on the floodplain of the lower Coeur d’Alene River or in 

Coeur d’Alene Lake. Furthermore, remediated riverbanks would be vulnerable to rapid recontamination by continuing 

deposition of about 6.9 +/- 5.3 cm/10y of sediment containing about 3400 +/- 990 ppm Pb (tables 3 and 4). 

Source Control by Periodic Removal of Sand Splays 

A sand splay (or crevasse splay) forms where floodwater transports sandy sediment onto the floodplain through a low 

pass in the levee. As the floodwater spreads onto the floodplain, it loses velocity, and sandy sediment is deposited to form a 

delta-like sand splay. The section of lead-rich sediments is more than 211 cm thick at sample site 93SBL31 on the large sandsplay in Strobl Marsh (Box and others, 2001). Oblique U.S. Forest Service air photos taken in June of 1933 indicate the splay 

was not present at that time, so we infer that the levee eroded and the sand splay began to form during the major winter flood of 

1933. At site 93SBL31 the depositional rate between 1933 and 1980 was greater than 34 cm/decade containing 4040 ppm Pb. 

The baseline depositional rate (from 1980 to 1993) was 4.6 cm/decade of sediment containing 4720 ppm Pb. 

Sand splays near Blackrock Slough and Strobl Marsh have been identified as sites that could serve as sediment traps, 

from which lead-rich sediments could be periodically removed following flood deposition events. The rationale for employing 

sand splays as sediment traps is that sand splays deliver lead-rich sediment from the river channel to the floodplain, where it

could be accessed for removal. However, the presumed benefits of such a removal strategy are not clear. Allowing a small 

fraction of mobilized sandy bedload to more easily escape the channel at a few localities would have an insignificant effect on
44 

the downstream bedload budget, neither reducing its volume nor reducing its metal content. Moreover, removing sediment from 

the existing sand splay will lower the elevation of the splay relative to the flood stage of the river, and allow a return to higher 

overflow-current velocities, and pre-1980 rates of sediment transport to and deposition on the sand splay. Since each sand splay 

is fed through a relatively narrow and well-defined low pass in the levee, rates of post-remedial deposition in and around the 

sand splay could be greatly reduced by blocking the low pass at the head of each splay. 

Local Dilution of Suspended Sediment with Low-Metal Sediment 

Concentrations of metals in sediment transported to and deposited on the floodplain of the lower Coeur d’Alene River 

result from the mixture of metal-rich and metal-poor source components. A possible approach to reducing metal concentrations 

in transported sediment is to increase the contribution of metal-poor source components, thereby diluting the concentration of 

metals in the mix. Uncontaminated sediment could be obtained locally from the thick section of unconsolidated sediments that 

underlies the relatively thin surficial section of contaminated sediments. Uncontaminated sediment could be placed in the path 

of (or injected into) moving water. For example, uncontaminated sediment could be placed at a distributary inlet, where it 

would tend to be carried into the lake or marsh fed by the distributary. Alternatively, uncontaminated sediment could be placed

along the margin of an eddy, or within a deep hole of the type that exists at tight bends in river channel (as indicated by a 

topographic map of the river bottom by AVISTA, unpublished data, 2004). Turbulent flow in an eddy or a river-bend hole 

would tend to loft and mix the sediment, while transporting it down-valley and onto the adjacent floodplain. This approach 

would take advantage of the power of moving water to mobilize, mix, transport, distribute, and deposit diluted sediment without

the use of heavy equipment on water-saturated wetlands. The section of lead-rich sediments would be immediately coated with 

relatively dilute metal-bearing sediment. This could be repeated during successive floods to build a cap of sufficient thickness 

to prevent ingestion of underlying lead-rich sediments by wildlife or humans. The capped area could then be isolated from the 

river to prevent recontamination. 

Riverbed Dredging as Source Control 

In the section on mobilization of sediment from the main stem of the Coeur d’Alene River, we estimated that about 50 

to 70 percent of the lead in suspended sediment transported past the Harrison gage is mobilized from the main-stem riverbed 

west of Cataldo. Bookstrom and others (2001) estimated that lead-rich sediments on the riverbed contain about 129 kt Pb, 

which is 14 times the 9 kt Pb contained in riverbank-wedge deposits west of Cataldo Landing. The area of sediments that is 

exposed to moving water on the riverbed is about 3.8 km2

 (Bookstrom and others, 2001), which is about 44 to 48 times the 

surface area of steep faces of riverbanks that are vulnerable to lateral erosion (0.079 km2

 to 0.087 km2 as indicated in table 16). 

Furthermore, riverbed sediments are relatively unconsolidated, whereas riverbank sediments are cemented by iron and 

manganese oxides. Riverbed deposits of lead-rich sediments therefore are much more vulnerable to mobilization, transport, redistribution, and re-deposition during episodes of high discharge than riverbank deposits of lead-rich sediments. 

Deposits of sediments stored in the river channel are particularly thick and high-grade along the Dudley reach of the 

river, which extends from the downstream toe of the sand bar at Cataldo Landing to Rose Lake (river segment R2 in figures 3 

and 4). The median thickness of sediments along the Dudley Reach is nearly 4 m, and the maximum thickness is over 8 m with 

a median of thickness-weighted average lead concentrations of nearly 10,000 ppm Pb (Bookstrom and others, 2001). Lead 

concentrations in sediment suspended during high-flow episodes commonly increase from about 2000 ppm Pb near Cataldo 

Landing to about 6000 ppm Pb at the lower end of the Dudley Reach (Box and others, in press). After the flood of February 

1996, we noted visible evidence of scour into well-layered sediments, previously deposited and stored in the river channel along 

the Dudley reach. 

Removal of the full thickness of metal-enriched sediment in the river channel for a portion of the Dudley Reach by 

dredging has been suggested as a strategy for reducing lead concentrations in future suspended and over-bank sediments along 

and downstream from the excavated reach. If dredging were to begin at Cataldo Landing, and progress down-river from there, 

the dredged river channel probably would re-fill with relatively dilute metal-bearing sediment, transported from the confluence

of the North and South Forks, and containing less than 2000 ppm Pb. If the entire Dudley reach, from Cataldo Landing to Rose 

Lake were dredged in this way, removed sediment in the river channel along this reach, with an average content of about 10,000 

ppm Pb, probably would be replaced by thinner deposits containing less than 2000 ppm Pb (a mixture of newly exposed premining bed sediment with the continued inflow of sediment from upstream). Sediment mobilized from the excavated reach 

would thus be reduced in metal content, as would sediments transported to and deposited on the floodplain along that reach. 

This lower-metal sediment would also act to dilute the concentrations of metals in active riverbed sediment for some distance 

downstream of the excavated reach. 

Although removal of the full thickness of metal-enriched sediment in the Dudley reach would reduce the metal 

concentrations of future flood-mobilized sediment in (and downstream of) that reach, the problem of continued inflow of less 

metal-enriched sediment from upstream must be considered. Would metal concentrations in future riverbank and floodplain 

sediment deposits after excavation of metal-enriched riverbed sediment become low enough to significantly reduce or eliminate 

impacts to wildlife and humans in that reach? Would periodic removal of post-excavation riverbed deposits in the excavated 
45 

reach provide additional benefits? The answers to either of those questions are uncertain, yet they are critical to predicting the 

effectiveness of either remedial action. 

Riverbed Source Control by In-Situ Stabilization 

In-situ stabilization of riverbed deposits of lead-rich sediments is another, potentially lower-cost method of riverbed 

source control. It might be possible to stabilize deposits of lead-rich sediments in the river channel by capping them in-place

with gravel too coarse to be mobilized during the highest probable discharges (about 7 ft/s). Cobble gravel could be obtained by 

surface mining the river channel or valley fill upstream from Cataldo Landing, and could be deposited over the river bottom 

downstream of Cataldo Landing to form an immobile gravel cap. If the gravel were obtained from the braided channel of the 

main-stem or the channel of the South Fork, lead-rich fines could be separated and placed in a repository, thus removing an 

upstream source of lead-rich sediment, while providing cleaned gravel for capping a downstream source of lead-rich sediment. 

If uncontaminated gravel were obtained from pre-mining valley-fill deposits along the main stem or the lower North Fork, the 

fines would not have to be removed, but could be deposited as a part of the gravel cap. Mobilization of these fines during highdischarge episodes would then dilute metal-rich sediments in transport. 

In-situ stabilization of lead-rich sediments in the river channel by capping with gravel would have two major 

advantages over removal: (1) Capping would isolate and prevent mobilization of the most highly lead-rich sediments at the base 

of the section of lead-rich sediments without disturbing them, and (2) capping would leave metal-enriched sediments in a 

predominantly reducing environment, where metals are geochemically immobile, whereas removal to a subaerial repository 

would place them in an oxidizing environment, where zinc, cadmium, copper, silver (and to a lesser degree, lead) are more 

vulnerable to geochemical mobilization. 

For capping of lead-rich sediments in the river channel with gravel to be effective, the gravel would have to be 

sufficiently coarse, thick, continuous, and widespread to protect underlying lead-rich sediments from vertical scour, interstitial 

plucking, and lateral erosion. The hydrologic effect of raising the channel floor and preventing erosion along the armored reach 

is uncertain and would require a pilot project or modeling to evaluate. To our knowledge, no studies have been done to evaluate

the feasibility, cost, or effectiveness of such an approach. 

Conclusions 

The median of thickness-weighted average lead concentrations of sediments deposited during the baseline interval is 

3100 ppm Pb, as compared to 5400 ppm Pb for sediments of the historic interval (based on data from 28 pairs of full baseline 

and full historic intervals of lead-rich sediments). The means of these two sample sets are statistically different. 

The median of pre-remedial baseline rates of deposition for lead-rich floodplain sediments is 3.6 cm/decade, as 

compared to 4.7 cm/decade for sediments of the historic floodplain-contamination interval (based on data from 46 pairs of full 

baseline and full historic time-stratigraphic intervals of lead-rich sediments). The probability that these two data sets represent 

statistically different populations is 87 percent. 

Based on data from 13 pairs of intervals with sub-equal thickness above and below the 1980 Mt St Helens volcanicash layer, the median of lead concentrations in sediments deposited during the baseline interval was 3300 ppm Pb, as compared 

to 4000 ppm Pb in sediments deposited between about 1968 and 1980 (after the 1968 cessation of tailings disposal to streams, 

but before deposition of the1980 volcanic ash layer). The probability that the means of these two data sets represent statistically 

different populations is 69 percent. 

On average, much of floor of the Coeur d’Alene River valley is flooded about every 2.5 y, and major floods with peak 

discharge of about 70,000 ft3

/s or more have occurred three times in the last 70 years, and twice in the last 30 years (in 1933, 

1974 and 1996). 

During floods, lead-rich sediment is deposited on the floodplain of the main stem of the Coeur d’Alene River. This 

occurs because lead-rich sediment continues to be mobilized and transported from large secondary sources of lead-rich 

sediments that were previously deposited in the South Fork drainage basin, and along the bed, banks, and levees of the main 

stem of the Coeur d’Alene River. 

The estimated tonnage of sediment mobilized annually from riverbanks along the main-stem west of Cataldo Landing 

is about 8 to 16 percent of the mean annual tonnage of lead in suspended sediment transported past the Harrison gage. The 

estimated tonnage of lead that is mobilized annually from large secondary sources of lead-rich sediments in the channel of the 

main stem of the Coeur d’Alene River is about 50 to 70 percent of the mean annual tonnage of lead in suspended sediment 

transported past the Harrison gage. An estimated 14 to 42 percent of the suspended sediment transported annually past the 

Harrison gage is therefore derived and transported from sources upstream from the Cataldo gage. 

However, mean annual tonnages of sediment transported past river gages vary widely from year to year, and river 

gages record the transport of only about half of the lead-rich sediment deposited annually on the floodplain. The gages have not 

recorded bed-material load or bedload during major floods with flow velocities sufficient to activate bedload transport, and the 

gages only record sediment transported within the span of the river channel. Therefore, the gages do not record sediment that is 

mobilized from the riverbed between gages, and deposited on the floodplain before floodwater returns to the river channel. 
46 

Our observations and data indicate that riverbanks and adjacent riparian areas will become recontaminated during 

high-water episodes after cleanup. Baseline rates of deposition on riverbanks average 6.9 +/- 5.3 cm/10y of lead-rich sediment,

containing 3400 +/- 990 ppm Pb. This can be expected to continue indefinitely after riverbank cleanup, unless ways can be 

found to prevent it or cope with it. 

Unless removed or stabilized, the dominant secondary source of lead-rich sediments in the channel of the main stem of 

the Coeur d’Alene River will continue to supply lead-rich sediment, to be transported down-valley, onto the floodplain, and into 

Coeur d’Alene Lake for centuries to come. 

These data and interpretations have important implications for remediation of areas impacted by deposition of metalenriched sediment in the basin. Remedial design must not only deal with contamination that occurred in the past, but also with

ongoing contamination that will continue into the future, unless controlled as a part of the remediation process. 

Acknowledgements 

We thank Keith Long, Donald Singer, Michael Zientek, and Charles Vita for helpful discussions and advice on 

statistical problems encountered in this study. Keith Long and Charles Vita reviewed the manuscript, and Gary Raines and 

Pamella Derkey reviewed the maps and the metadata, all of which were improved in response to their comments and 

suggestions. Thomas Frost reviewed several revisions of the manuscript, and offered many helpful suggestions. 

The Mineral Resources Program, Geologic Division, U.S. Geological Survey provided most of the funding and 

support required to produce this report. The Natural Resource Damage Assessment for the Coeur d’Alene Basin funded field

work of Robert Fousek through a contract with the Water Resources Division, U.S. Geological Survey. The Coeur d’Alene 

Tribe digitized the surficial geologic base map. 

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Appendix 1. Data Table 
49 

Appendix 2. Metadata 
Appendix 1. Table A. Data 

SAMP_NO DATA_SET REF UTM_E UTM_N SYS ENV SEG SEC AAMTD ASSAY_INT M_TO_R FLUV_FTR

91SBKF2 UI/Bender/89 Bender (1991) 532832 5262904 Llm FB Mc fna correl 2 span 1693 lat lk limetic

M91A UI/Hoffman/91 Hoffmann (1995) 531167 5257415 Ldd FB Mc pna correl 2 span 897 lat lk delta

T91A UI/Hoffmann/91 Hoffmann (1995) 520987 5259526 Llm FB Lc nfna correl 2 span 603 lat lk limetic

M92CS UI/Hoffmann/92 Hoffmann (1995) 531355 5257320 Llm FB Mc p Cs isotp na 1235 lat lk limetic

93ABM2 USGS/GD/93 Box and others (2001) 529444 5258540 RU LV La f msr cm strat span 22 outside bnk

93ABM4 USGS/GD/93 Box and others (2001) 530875 5258592 U LV Mc f msr cm strat span 15 inside rlv

93CSC03 USGS/GD/93 Box and others (2001) 547703 5266465 RU LV Ub p msr cm strat span 1 outside bnk

93SBB21 USGS/GD/93 Box and others (2001) 520657 5258947 RU LV Lc f msr cm strat span 1 outside bnk

93SBB22 USGS/GD/93 Box and others (2001) 522317 5258253 P FB Lc f msr cm strat span 81 lat marsh

93SBB23 USGS/GD/93 Box and others (2001) 522333 5258176 RU LV Lb f msr cm strat span 5 straight bnk

93SBC10 USGS/GD/93 Box and others (2001) 549480 5265355 RU LV Ub f msr cm strat span 8 inside bnk

93SBC15 USGS/GD/93 Box and others (2001) 548107 5265684 U LV Ua p msr cm strat span 4 alluv terrace

93SBC39 USGS/GD/93 Box and others (2001) 554595 5266545 RU LV Ua f msr cm strat span 8 outside bnk

93SBC40 USGS/GD/93 Box and others (2001) 536505 5243065 RU LV SJRV loPb msr cm strat span 10 st joe bnk

93SBL27 USGS/GD/93 Box and others (2001) 535274 5263833 RU LV Mb f msr cm strat span 0 outside bnk

93SBL27B USGS/GD/93 Box and others (2001) 535206 5263729 U LV Mb f msr cm strat span 57 outside rlv

93SBL30 USGS/GD/93 Box and others (2001) 534930 5263450 U LV Mb f msr cm strat span 366 outside rlv

93SBL31 USGS/GD/93 Box and others (2001) 534327 5262268 U LV Mb p msr cm strat span 333 splay

93SBL32 USGS/GD/93 Box and others (2001) 534428 5261668 U LV Mb f msr cm strat span 114 inside rlv

93SBR13 USGS/GD/93 Box and others (2001) 541836 5264028 RU LV Uc p msr cm strat span 9 inside bnk

94GID3 USGS/GD/94 Box and others (2001) 535357 5262890 U LV Mb f msr cm strat span 43 inside rlv

94GID5 USGS/GD/94 Box and others (2001) 535320 5262892 P FB Mb f msr cm intrvl>aa 67 lat marsh

94GID6 USGS/GD/94 Box and others (2001) 535274 5262893 P FB Mb f msr cm intrvl>aa 103 lat marsh

94xb08 USGS/GD/94 Bookstrom unpub data (1994) 520645 5258923 RU LV Lc f msr cm strat span 0 outside bnk

94xb19 USGS/GD/94 Bookstrom unpub data (1994) 520742 5258871 RU LV Lb p msr cm strat span 0 inside bnk

94xb22 USGS/GD/94 Bookstrom unpub data (1994) 520695 5258958 RU LV Lc p msr cm strat span 0 outside bnk

94xb27 USGS/GD/94 Bookstrom unpub data (1994) 520725 5258970 RU LV Lc f msr cm strat span 0 outside bnk

94xb33 USGS/GD/94 Bookstrom unpub data (1994) 520933 5258874 RU LV Lb f msr cm strat span 0 straight bnk

94xc03 USGS/GD/94 Bookstrom unpub data (1994) 547092 5266337 RU LV Uc f msr cm strat span 0 inside bnk

94xl04 USGS/GD/94 Bookstrom unpub data (1994) 536821 5264394 RU LV Ma p msr cm strat span 4 inside bnk

94xl13 USGS/GD/94 Bookstrom unpub data (1994) 536635 5263927 RU LV Ma f msr cm strat span 1 straight bnk

94xr06 USGS/GD/94 Bookstrom unpub data (1994) 546489 5266116 RU LV Uc f msr cm strat span 1 outside bnk

94xr12 USGS/GD/94 Bookstrom unpub data (1994) 546388 5265952 RU LV Uc f msr cm strat span 1 straight bnk

94xr17 USGS/GD/94 Bookstrom unpub data (1994) 546262 5265503 RU LV Uc p msr cm strat span 1 straight bnk

94xr25 USGS/GD/94 Bookstrom unpub data (1994) 546253 5265005 RU LV Uc p msr cm strat span 1 inside bnk

94xr30 USGS/GD/94 Bookstrom unpub data (1994) 546076 5264816 RU LV Uc f msr cm strat span 1 straight bnk

94xr36 USGS/GD/94 Bookstrom unpub data (1994) 544235 5265435 RU LV Uc f msr cm strat span 2 inside bnk

94xr41 USGS/GD/94 Bookstrom unpub data (1994) 544144 5265468 RU LV Uc p msr cm strat span 0 inside bnk

94xr44 USGS/GD/94 Bookstrom unpub data (1994) 543392 5265407 RU LV Uc p msr cm strat span 1 straight bnk

1
Appendix 1. Table A. Data 

SAMP_NO

91SBKF2

M91A

T91A

M92CS

93ABM2

93ABM4

93CSC03

93SBB21

93SBB22

93SBB23

93SBC10

93SBC15

93SBC39

93SBC40

93SBL27

93SBL27B

93SBL30

93SBL31

93SBL32

93SBR13

94GID3

94GID5

94GID6

94xb08

94xb19

94xb22

94xb27

94xb33

94xc03

94xl04

94xl13

94xr06

94xr12

94xr17

94xr25

94xr30

94xr36

94xr41

94xr44

ASH_CM AA_CM AA_10Y AA_CM_10Y BA_CM BA_10Y BA_CM_10Y SR_AABA JBA_CM JBA_AA BA1_CM PBR_CM PBR_10Y

0.0 5.0 1.1 4.5 45.0 7.7 5.8 0.77 5.0 1.0 4.5 50 8.8

0.0 4.0 1.1 3.6 48.0 7.7 6.2 0.58 4.0 1.0 4.0 52 8.8

0.0 3.0 1.1 2.7 42.0 7.7 5.5 0.50 2.7 1.0 3.0 48 8.8

0.0 5.2 1.2 4.3 26.8 2.9 9.2 0.47 4.8 0.9 4.8 32 4.1

1.0 10.0 1.3 7.7 86.0 7.7 11.2 0.69 11.0 1.1 11.0 97 9.0

1.0 12.0 1.3 9.2 63.0 7.7 8.2 1.13 14.0 1.2 -999.0 76 9.0

0.5 6.0 1.3 4.6 249.5 7.7 -999.0 -999.00 3.5 0.6 -999.0 256 9.0

1.0 9.0 1.3 6.9 101.0 7.7 13.1 0.53 -999.0 -999.0 -999.0 111 9.0

0.5 4.0 1.3 3.1 24.5 7.7 3.2 0.97 4.0 1.0 4.0 29 9.0

1.0 5.0 1.3 3.8 47.0 7.7 6.1 0.63 6.0 1.2 -999.0 53 9.0

0.5 3.0 1.3 2.3 96.5 7.7 12.5 0.18 26.5 8.8 -999.0 100 9.0

1.0 15.0 1.3 11.5 245.0 7.7 -999.0 -999.00 19.0 1.3 -999.0 261 9.0

0.5 5.0 1.3 3.8 26.5 7.7 3.4 1.12 4.5 0.9 4.5 32 9.0

1.0 10.0 1.3 7.7 -999.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 125 -99.9

0.5 7.0 1.3 5.4 52.5 7.7 6.8 0.79 11.5 1.6 -999.0 60 9.0

1.0 4.0 1.3 3.1 64.0 7.7 8.3 0.37 11.0 2.8 -999.0 69 9.0

0.5 4.0 1.3 3.1 32.5 7.7 4.2 0.73 4.5 1.1 4.5 37 9.0

0.5 6.0 1.3 4.6 204.5 7.7 -999.0 -999.00 11.5 1.9 -999.0 211 9.0

0.5 3.0 1.3 2.3 20.5 7.7 2.7 0.87 7.0 2.3 -999.0 24 9.0

1.0 15.0 1.3 11.5 275.0 7.7 -999.0 -999.00 36.0 2.4 -999.0 291 9.0

0.5 3.0 1.4 2.1 153.5 7.7 19.9 0.11 9.0 3.0 -999.0 157 9.1

0.5 5.0 1.4 3.6 37.5 7.7 4.9 0.73 -999.0 -999.0 -999.0 43 9.1

1.0 3.0 1.4 2.1 16.0 7.7 2.1 1.03 -999.0 -999.0 -999.0 20 9.1

-999.0 9.0 1.4 6.4 102.0 7.7 13.2 0.49 -999.0 -999.0 -999.0 111 9.1

-999.0 10.0 1.4 7.1 160.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 170 9.1

-999.0 15.0 1.4 10.7 130.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 145 9.1

-999.0 17.0 1.4 12.1 95.0 7.7 12.3 0.98 -999.0 -999.0 -999.0 112 9.1

-999.0 5.0 1.4 3.6 20.0 7.7 2.6 1.38 -999.0 -999.0 -999.0 25 9.1

-999.0 40.0 1.4 28.6 120.0 7.7 15.6 1.83 -999.0 -999.0 -999.0 160 9.1

-999.0 10.0 1.4 7.1 290.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 300 9.1

-999.0 15.0 1.4 10.7 128.0 7.7 16.6 0.64 -999.0 -999.0 -999.0 143 9.1

-999.0 20.0 1.4 14.3 80.0 7.7 10.4 1.38 -999.0 -999.0 -999.0 100 9.1

-999.0 7.0 1.4 5.0 273.0 7.7 35.5 0.14 -999.0 -999.0 -999.0 280 9.1

-999.0 17.0 1.4 12.1 118.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 135 9.1

-999.0 22.0 1.4 15.7 223.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 245 9.1

-999.0 13.0 1.4 9.3 167.0 7.7 21.7 0.43 -999.0 -999.0 -999.0 180 9.1

-999.0 7.0 1.4 5.0 34.0 7.7 4.4 1.13 -999.0 -999.0 -999.0 41 9.1

-999.0 10.0 1.4 7.1 163.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 173 9.1

-999.0 5.0 1.4 3.6 175.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 180 9.1

2
Appendix 1. Table A. Data 

SAMP_NO

91SBKF2

M91A

T91A

M92CS

93ABM2

93ABM4

93CSC03

93SBB21

93SBB22

93SBB23

93SBC10

93SBC15

93SBC39

93SBC40

93SBL27

93SBL27B

93SBL30

93SBL31

93SBL32

93SBR13

94GID3

94GID5

94GID6

94xb08

94xb19

94xb22

94xb27

94xb33

94xc03

94xl04

94xl13

94xr06

94xr12

94xr17

94xr25

94xr30

94xr36

94xr41

94xr44

PBR_CM_10Y PBR_PB AA_PB BA_PB PB_AABA JBA_PB BA1_PB PBAA_BA1 SAMP_NO

5.7 11050 4400 12000 0.37 4100 4100 1.07 91SBKF2

5.9 5012 5200 5000 1.04 5900 5900 0.88 M91A

5.5 7593 2800 7800 0.36 2800 2800 1.00 T91A

7.8 -999 -999 -999 -999.00 -999 -999 -999.00 M92CS

10.8 4698 4200 4756 0.88 4000 4000 1.05 93ABM2

8.4 5438 3700 5767 0.64 3875 -999 -999.00 93ABM4

28.4 14129 3211 -999 -999.00 6804 -999 0.47 93CSC03

12.3 4446 3090 4566 0.68 -999 -999 -999.00 93SBB21

3.2 6313 1180 7154 0.16 2620 2620 0.45 93SBB22

5.9 5038 3950 5153 0.77 2530 -999 -999.00 93SBB23

11.1 8297 3310 8452 0.39 3820 -999 -999.00 93SBC10

29.0 6244 740 -999 -999.00 1470 -999 -999.00 93SBC15

3.6 3341 3315 3519 0.94 2820 2820 1.18 93SBC39

-999.0 -999 21 23 0.91 -999 -999 -999.00 93SBC40

6.7 4523 4610 4511 1.02 4230 -999 -999.00 93SBL27

7.7 5200 4460 5246 0.85 4910 -999 -999.00 93SBL27B

4.1 5658 5200 5715 0.91 5150 5150 1.01 93SBL30

23.4 3937 4720 -999 -999.00 4300 -999 -999.00 93SBL31

2.7 9968 2650 11044 0.24 4800 -999 -999.00 93SBL32

32.3 5362 5350 -999 -999.00 5650 -999 -999.00 93SBR13

17.3 4512 4935 -999 -999.00 4070 -999 -999.00 94GID3

4.7 5408 -999 -999 -999.00 -999 -999 -999.00 94GID5

2.2 7210 -999 -999 -999.00 -999 -999 -999.00 94GID6

12.2 -999 -999 -999 -999.00 -999 -999 -999.00 94xb08

18.7 -999 -999 -999 -999.00 -999 -999 -999.00 94xb19

15.9 -999 -999 -999 -999.00 -999 -999 -999.00 94xb22

12.3 -999 -999 -999 -999.00 -999 -999 -999.00 94xb27

2.7 -999 -999 -999 -999.00 -999 -999 -999.00 94xb33

17.6 -999 -999 -999 -999.00 -999 -999 -999.00 94xc03

33.0 -999 -999 -999 -999.00 -999 -999 -999.00 94xl04

15.7 -999 -999 -999 -999.00 -999 -999 -999.00 94xl13

11.0 -999 -999 -999 -999.00 -999 -999 -999.00 94xr06

30.8 -999 -999 -999 -999.00 -999 -999 -999.00 94xr12

14.8 -999 -999 -999 -999.00 -999 -999 -999.00 94xr17

26.9 -999 -999 -999 -999.00 -999 -999 -999.00 94xr25

19.8 -999 -999 -999 -999.00 -999 -999 -999.00 94xr30

4.5 -999 -999 -999 -999.00 -999 -999 -999.00 94xr36

19.0 -999 -999 -999 -999.00 -999 -999 -999.00 94xr41

19.8 -999 -999 -999 -999.00 -999 -999 -999.00 94xr44

3
Appendix 1. Table A. Data 

SAMP_NO DATA_SET REF UTM_E UTM_N SYS ENV SEG SEC AAMTD ASSAY_INT M_TO_R FLUV_FTR

94xr49 USGS/GD/94 Bookstrom unpub data (1994) 543190 5265382 RU LV Uc p msr cm strat span 1 straight bnk

94xr53 USGS/GD/94 Bookstrom unpub data (1994) 543378 5265520 RU LV Uc p msr cm strat span 0 straight bnk

94xr64 USGS/GD/94 Bookstrom unpub data (1994) 542667 5265014 RU LV Uc f msr cm strat span 2 inside bnk

94xr70 USGS/GD/94 Bookstrom unpub data (1994) 542414 5264366 RU LV Uc f msr cm strat span 3 straight bnk

94xr73 USGS/GD/94 Bookstrom unpub data (1994) 542407 5264357 RU LV Uc f msr cm strat span 4 straight bnk

94xr81 USGS/GD/94 Bookstrom unpub data (1994) 541020 5264420 RU LV Uc p msr cm strat span 1 straight bnk

94xr88 USGS/GD/94 Bookstrom unpub data (1994) 540548 5264633 RU LV Uc f msr cm strat span 2 straight bnk

94xr98 USGS/GD/94 Bookstrom unpub data (1994) 539776 5264882 RU LV Uc p msr cm strat span 0 outside bnk

94xra15 USGS/GD/94 Bookstrom unpub data (1994) 539515 5264615 RU LV Ma f msr cm strat span 3 inside bnk

94xra21 USGS/GD/94 Bookstrom unpub data (1994) 539071 5264498 RU LV Ma p msr cm strat span 1 inside bnk

94xra24 USGS/GD/94 Bookstrom unpub data (1994) 538204 5264692 RU LV Ma f msr cm strat span 1 inside bnk

K95A USGS/GD/95 Box and others (2001) 533152 5262100 Ldd FB Mc fna nd na 840 lat lk delta

96K114E USGS/GD/96 Box and others (2001) 535490 5262885 U LV Mb p msr cm strat span 209 outside rlv

96K178E USGS/GD/96 Box and others (2001) 535555 5262882 U LV Mb p msr cm strat span 240 outside rlv

96K89E USGS/GD/96 Box and others (2001) 535474 5262886 U LV Mb f msr cm strat span 1 outside rlv

96LD-105S USGS/GD/96 Box and others (2001) 544095 5265464 U LV Uc f msr cm strat span 136 inside rlv

T98C-1 USGS/GD/98 Box and others (2001) 554982 5266215 P FB Ua loPb msr cm strat span 470 lat marsh

T98C-12 USGS/GD/98 Box and others (2001) 548414 5265979 U LV Ub p msr cm strat span 350 alluv terrace

T98C-15 USGS/GD/98 Box and others (2001) 554438 5266433 P FB Ub f msr cm strat span 100 lat marsh

T98C-16 USGS/GD/98 Box and others (2001) 548325 5265879 U LV Ub p msr cm aatp, ba1btm 240 alluv terrace

T98C-17 USGS/GD/98 Box and others (2001) 547855 5266330 U LV Ub f msr cm strat spot 45 inside rlv

T98C-18 USGS/GD/98 Box and others (2001) 549029 5266296 U LV Ub f msr cm strat spot 1025 alluv terrace

T98C-21 USGS/GD/98 Box and others (2001) 548101 5266521 P FB Ub p msr cm aatp, ba1btm 440 lat marsh

T98C-25 USGS/GD/98 Box and others (2001) 550599 5265753 U LV Ub loPb msr cm strat spot 450 alluv terrace

T98C-4 USGS/GD/98 Box and others (2001) 554640 5266523 U LV Ua loPb msr cm strat spot 50 alluv terrace

T98C-5 USGS/GD/98 Box and others (2001) 554544 5266345 P FB Ua f msr cm strat spot 200 lat marsh

T98C-6 USGS/GD/98 Box and others (2001) 551049 5266713 U LV Ub f msr cm strat spot 14 alluv terrace

T98C-7 USGS/GD/98 Box and others (2001) 551215 5266659 U LV Ub p msr cm strat spot 280 alluv terrace

T98C-8 USGS/GD/98 Box and others (2001) 550294 5266184 U LV Ub p msr cm strat spot 125 alluv terrace

T98L-36 USGS/GD/98 Box and others (2001) 536966 5264051 U LV Ma p msr cm aatp, ba1btm 330 splay

T98M-43 USGS/GD/98 Box and others (2001) 532442 5259956 U LV Mc f msr cm strat spot 150 inside rlv

T98R-13 USGS/GD/98 Box and others (2001) 546142 5266950 PA FB Uc f msr cm aatp, ba1btm 890 marsh artif

T98R-14 USGS/GD/98 Box and others (2001) 547013 5267146 UA LV Uc p msr cm aatp, ba1btm 660 uplnd artif

T98R-28 USGS/GD/98 Box and others (2001) 538865 5264852 U LV Ma f msr cm aatp, ba1btm 230 distrib lv

T98R-30 USGS/GD/98 Box and others (2001) 537972 5264424 U LV Ma f msr cm aatp, ba1btm 200 inside rlv

T98R-31 USGS/GD/98 Box and others (2001) 546916 5266067 U LV Uc p msr cm aatp, ba1btm 120 inside rlv

H90-123 USGS/WRD/90 Horowitz and others (1995) 513590 5255470 DLT FB DLTT f msr cm 1-2.5 span 1800 main delta

BL9323 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 520589 5259868 P FB Lc loPb msr in 0-5aaba, 5-15 911 lat marsh

BL9333 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 522869 5258382 RU LV Lb p msr in 0-5aaba, 5-15 0 outside bnk

4
Appendix 1. Table A. Data 

SAMP_NO

94xr49

94xr53

94xr64

94xr70

94xr73

94xr81

94xr88

94xr98

94xra15

94xra21

94xra24

K95A

96K114E

96K178E

96K89E

96LD-105S

T98C-1

T98C-12

T98C-15

T98C-16

T98C-17

T98C-18

T98C-21

T98C-25

T98C-4

T98C-5

T98C-6

T98C-7

T98C-8

T98L-36

T98M-43

T98R-13

T98R-14

T98R-28

T98R-30

T98R-31

H90-123

BL9323

BL9333

ASH_CM AA_CM AA_10Y AA_CM_10Y BA_CM BA_10Y BA_CM_10Y SR_AABA JBA_CM JBA_AA BA1_CM PBR_CM PBR_10Y

-999.0 7.0 1.4 5.0 143.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 150 9.1

-999.0 9.0 1.4 6.4 111.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 120 9.1

-999.0 16.0 1.4 11.4 74.0 7.7 9.6 1.19 -999.0 -999.0 -999.0 90 9.1

-999.0 25.0 1.4 17.9 35.0 7.7 4.5 3.93 -999.0 -999.0 -999.0 60 9.1

-999.0 15.0 1.4 10.7 8.0 7.7 1.0 10.31 -999.0 -999.0 -999.0 23 9.1

-999.0 12.0 1.4 8.6 168.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 180 9.1

-999.0 12.0 1.4 8.6 150.0 7.7 19.5 0.44 -999.0 -999.0 -999.0 162 9.1

-999.0 4.0 1.4 2.9 89.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 93 9.1

-999.0 12.0 1.4 8.6 11.0 7.7 1.4 6.00 -999.0 -999.0 -999.0 23 9.1

-999.0 10.0 1.4 7.1 213.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 223 9.1

-999.0 4.0 1.4 2.9 14.0 7.7 1.8 1.57 -999.0 -999.0 -999.0 18 9.1

0.0 -999.0 1.5 -999.0 -999.0 7.7 -999.0 -999.0 -999.0 -999.0 -999.0 193 9.2

1.0 33.0 1.6 20.6 141.0 7.7 -999.0 -999.00 28.0 0.8 -999.0 175 9.3

1.0 18.0 1.6 11.3 121.0 7.7 -999.0 -999.00 16.0 0.9 16.0 140 9.3

1.0 22.0 1.6 13.8 109.0 7.7 14.2 0.97 26.0 1.2 -999.0 132 9.3

0.5 5.0 1.6 3.1 28.5 7.7 3.7 0.84 12.5 2.5 -999.0 34 9.3

1.0 3.0 1.8 1.7 -999.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 -999.0 9.5

1.0 5.0 1.8 2.8 74.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 80 9.5

0.2 4.0 1.8 2.2 41.8 7.7 5.4 0.41 -999.0 -999.0 -999.0 46 9.5

0.2 9.9 1.8 5.5 199.9 7.7 -999.0 -999.00 9.9 1.0 9.9 210 9.5

1.0 8.0 1.8 4.4 83.0 7.7 10.8 0.41 -999.0 -999.0 -999.0 92 9.5

1.0 3.0 1.8 1.7 27.0 7.7 3.5 0.48 -999.0 -999.0 -999.0 31 9.5

1.0 14.0 1.8 7.8 185.0 7.7 -999.0 -999.00 6.0 0.4 -999.0 200 9.5

1.5 5.0 1.8 2.8 -999.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 175 9.5

1.0 6.0 1.8 3.3 -999.0 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 90 9.5

0.2 -999.0 1.8 2.8 104.8 7.7 13.6 0.20 -999.0 -999.0 -999.0 110 9.5

0.2 3.0 1.8 1.7 12.8 7.7 1.7 1.00 -999.0 -999.0 -999.0 16 9.5

0.2 5.0 1.8 2.8 19.8 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 25 9.5

0.2 3.0 1.8 1.7 19.8 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 23 9.5

0.5 16.5 1.8 9.2 178.0 7.7 -999.0 -999.00 8.0 0.5 -999.0 195 9.5

0.5 2.0 1.8 1.1 27.5 7.7 3.6 0.31 -999.0 -999.0 -999.0 30 9.5

4.0 6.0 1.8 3.3 25.0 7.7 3.2 1.03 14.0 2.3 -999.0 35 9.5

0.5 3.0 1.8 1.7 116.5 7.7 -999.0 -999.00 17.0 5.7 -999.0 120 9.5

1.0 2.5 1.8 1.4 26.5 7.7 3.4 0.40 8.0 3.2 -999.0 30 9.5

0.9 4.0 1.8 2.2 9.1 7.7 1.2 1.88 4.0 1.0 4.0 14 9.5

1.0 5.5 1.8 3.1 183.5 7.7 -999.0 -999.00 14.5 2.6 -999.0 190 9.5

1.5 20.5 1.0 20.5 88.0 7.7 11.4 1.79 16.5 0.8 -999.0 110 8.7

0.6 3.2 1.3 2.5 -999.0 7.7 -999.0 -999.00 1.2 0.4 -999.0 15 9.0

0.3 1.0 1.3 0.8 13.4 7.7 -999.0 -999.00 3.7 3.7 -999.0 15 9.0

5
Appendix 1. Table A. Data 

SAMP_NO

94xr49

94xr53

94xr64

94xr70

94xr73

94xr81

94xr88

94xr98

94xra15

94xra21

94xra24

K95A

96K114E

96K178E

96K89E

96LD-105S

T98C-1

T98C-12

T98C-15

T98C-16

T98C-17

T98C-18

T98C-21

T98C-25

T98C-4

T98C-5

T98C-6

T98C-7

T98C-8

T98L-36

T98M-43

T98R-13

T98R-14

T98R-28

T98R-30

T98R-31

H90-123

BL9323

BL9333

PBR_CM_10Y PBR_PB AA_PB BA_PB PB_AABA JBA_PB BA1_PB PBAA_BA1 SAMP_NO

16.5 -999 -999 -999 -999.00 -999 -999 -999.00 94xr49

13.2 -999 -999 -999 -999.00 -999 -999 -999.00 94xr53

9.9 -999 -999 -999 -999.00 -999 -999 -999.00 94xr64

6.6 -999 -999 -999 -999.00 -999 -999 -999.00 94xr70

2.5 -999 -999 -999 -999.00 -999 -999 -999.00 94xr73

19.8 -999 -999 -999 -999.00 -999 -999 -999.00 94xr81

17.8 -999 -999 -999 -999.00 -999 -999 -999.00 94xr88

10.2 -999 -999 -999 -999.00 -999 -999 -999.00 94xr98

2.5 -999 -999 -999 -999.00 -999 -999 -999.00 94xra15

24.5 -999 -999 -999 -999.00 -999 -999 -999.00 94xra21

2.0 -999 -999 -999 -999.00 -999 -999 -999.00 94xra24

21.0 -999 -999 -999 -999.00 -999 -999 -999.00 K95A

18.8 6010 5554 -999 -999.00 5913 -999 0.94 96K114E

15.1 6230 5665 -999 -999.00 6735 6735 0.84 96K178E

14.2 5256 5104 5287 0.97 5290 -999 -999.00 96K89E

3.7 6931 3858 7472 0.52 4380 -999 -999.00 96LD-105S

-999.0 -999 712 600 1.19 -999 -999 -999.00 T98C-1

8.4 4720 -999 -999 -999.00 4720 -999 -999.00 T98C-12

4.8 13369 7460 13940 0.54 -999 -999 -999.00 T98C-15

22.1 5876 1960 -999 -999.00 4150 4150 0.47 T98C-16

9.7 8347 1630 8991 0.18 7550 -999 -999.00 T98C-17

3.3 7675 1380 8364 0.16 -999 -999 -999.00 T98C-18

21.1 3116 1870 -999 -999.00 3290 -999 0.57 T98C-21

-999.0 -999 839 325 2.58 -999 -999 -999.00 T98C-25

-999.0 -999 -999 -999 -999.00 -999 -999 -999.00 T98C-4

11.6 3650 -999 3695 -999.00 -999 -999 -999.00 T98C-5

1.7 1890 1890 1890 1.00 -999 -999 -999.00 T98C-6

2.6 4300 4300 -999 -999.00 -999 -999 -999.00 T98C-7

2.4 6160 6160 -999 -999.00 -999 -999 -999.00 T98C-8

20.5 4533 5100 -999 -999.00 4495 -999 1.13 T98L-36

3.2 3003 1620 3104 0.52 5110 -999 -999.00 T98M-43

3.7 4750 1500 5437 0.28 6050 -999 -999.00 T98R-13

12.6 3017 1610 -999 -999.00 2360 -999 -999.00 T98R-14

3.2 7537 6130 7668 0.80 9810 -999 -999.00 T98R-28

1.5 4406 1820 5506 0.33 5440 5440 0.33 T98R-30

20.0 10215 1520 -999 -999.00 3980 -999 -999.00 T98R-31

12.6 7096 5380 7507 0.71 4436 -999 1.21 H90-123

-999.0 -999 285 355 0.80 355 -999 0.80 BL9323

1.7 3183 3000 -999 -999.00 2900 -999 -999.00 BL9333

6
Appendix 1. Table A. Data 

SAMP_NO DATA_SET REF UTM_E UTM_N SYS ENV SEG SEC AAMTD ASSAY_INT M_TO_R FLUV_FTR

BL9339 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 523502 5258644 U LV Lb p msr in 0-5aaba, 5-15 264 distrib lv

BL9345 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 525268 5257143 RU LV Lb p msr in 0-5aaba, 5-15 19 outside bnk

BL9346 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 524865 5257941 U LV Lb p msr in 0-5aaba, 5-15 32 straight rlv

BL9347 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 524190 5259138 Llt FB Lb p msr in 0-5aaba, 5-15 912 lat lk littoral

BL9353 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 525770 5257540 P FB Lb p msr in 0-5aaba, 5-15 350 lat marsh

BL9354 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 525540 5256770 RU LV Lb p msr in 0-5aaba, 5-15 0 outside bnk

BL9355 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 525673 5255911 Llt FB Lb p msr in 0-5aaba, 5-15 307 lat lk littoral

BL9360 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 526820 5255638 P FB La loPb msr in 0-5aaba, 5-15 454 lat marsh

BL9369 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 527358 5258230 Llt FB La f msr in 0-5aaba, 5-15 1377 lat lk littoral

BL9370 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 527614 5256597 U LV La p msr in 0-5aaba, 5-15 119 inside rlv

BL9371 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 527949 5256503 U LV La p msr in 0-5aaba, 5-15 8 outside rlv

C93235 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 547755 5266574 U LV Uc p msr in 0-5aaba, 5-15 37 outside rlv

C93236 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 547304 5266260 RU LV Uc p msr in 0-5aaba, 5-15 6 outside bnk

C93243 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 548224 5265680 RU LV Uc p msr in 0-5aaba, 5-15 5 straight bnk

C93244 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 548238 5266483 U LV Ub p msr in 0-5aaba, 5-15 414 alluv terrace

C93249 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 549118 5266463 U LV Ub p msr in 0-5aaba, 5-15 1033 alluv terrace

C93250 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 549225 5266186 U LV Ub p msr in 0-5aaba, 5-15 825 alluv terrace

C93256 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 550802 5264930 P FB Ub loPb msr in 0-5aaba, 5-15 1000 lat marsh

C93273 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 552608 5268250 U LV Ua f msr in 0-5aaba, 5-15 173 alluv terrace

C93280 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 553175 5268348 U LV Ua p msr in 0-5aaba, 5-15 149 alluv terrace

C93281 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 553709 5267056 U LV Ua p msr in 0-5aaba, 5-15 0 alluv terrace

C93288 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 554878 5266848 U LV Ua p msr in 0-5aaba, 5-15 66 alluv terrace

C93296 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 555834 5270014 U LV NF loPb msr in 0-5aaba, 5-15 87 alluv terrace

C93307 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 556204 5268438 RU LV NF loPb msr in 0-5aaba, 5-15 0 n fk bnk

H934.2 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 518000 5256575 Llt FB Lc p msr in 0-5aaba, 5-15 170 lat lk littoral

L93118 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 533262 5261100 U LV Mc p msr in 0-5aaba, 5-15 10 inside rlv

L93119 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 533010 5261649 U LV Mc p msr in 0-5aaba, 5-15 488 distrib lv

L93121 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 532930 5264182 P FB Mc f msr in 0-5aaba, 5-15 2373 lat marsh

L93128 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 534326 5261476 U LV Mc p msr in 0-5aaba, 5-15 19 straight rlv

L93135 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 534890 5261603 P FB Mb p msr in 0-5aaba, 5-15 103 lat marsh

L93137 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 535146 5263795 P FB Mb p msr in 0-5aaba, 5-15 122 lat marsh

L93154 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 537037 5262913 Llt FB Ma loPb msr in 0-5aaba, 5-15 457 lat lk littoral

L93156 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 537069 5264488 U LV Ma p msr in 0-5aaba, 5-15 35 outside rlv

L93162 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 537428 5263873 U LV Ma p msr in 0-5aaba, 5-15 126 outside rlv

M93104 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 532255 5260499 P FB Mc p msr in 0-5aaba, 5-15 574 lat marsh

M93106 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 531496 5259395 P FB Mc p msr in 0-5aaba, 5-15 260 lat marsh

M93107 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 532169 5258253 P FB Mc loPb msr in 0-5aaba, 5-15 434 lat marsh

M93108 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 531523 5257139 Llt FB Mc p msr in 0-5aaba, 5-15 1410 lat lk littoral

M93109 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 531763 5256085 P FB Mc loPb msr in 0-5aaba, 5-15 2330 lat marsh

7
Appendix 1. Table A. Data 

SAMP_NO

BL9339

BL9345

BL9346

BL9347

BL9353

BL9354

BL9355

BL9360

BL9369

BL9370

BL9371

C93235

C93236

C93243

C93244

C93249

C93250

C93256

C93273

C93280

C93281

C93288

C93296

C93307

H934.2

L93118

L93119

L93121

L93128

L93135

L93137

L93154

L93156

L93162

M93104

M93106

M93107

M93108

M93109

ASH_CM AA_CM AA_10Y AA_CM_10Y BA_CM BA_10Y BA_CM_10Y SR_AABA JBA_CM JBA_AA BA1_CM PBR_CM PBR_10Y

1.3 5.1 1.3 3.9 7.7 7.7 -999.0 -999.00 8.6 1.7 -999.0 15 9.0

0.3 1.9 1.3 1.5 12.8 7.7 -999.0 -999.00 2.8 1.5 -999.0 15 9.0

-999.0 1.9 1.3 1.5 13.1 7.7 -999.0 -999.00 3.1 1.6 -999.0 15 9.0

1.3 5.1 1.3 3.9 9.9 7.7 -999.0 -999.00 8.6 1.7 -999.0 15 9.0

-999.0 -999.0 -99.9 -999.0 -999.0 -99.9 -999.0 -999.00 -999.0 -999.0 -999.0 -999.0 -99.9

0.7 5.1 1.3 3.9 9.3 7.7 -999.0 -999.00 9.2 1.8 -999.0 15 9.0

0.3 1.6 1.3 1.2 13.4 7.7 -999.0 -999.00 3.1 1.9 -999.0 15 9.0

0.3 1.9 1.3 1.5 -999.0 7.7 -999.0 -999.00 2.8 1.5 -999.0 -999.0 9.0

0.5 3.8 1.3 2.9 4.5 7.7 0.6 4.99 0.7 0.2 -999.0 5 9.0

0.3 3.8 1.3 2.9 10.6 7.7 -999.0 -999.00 0.8 0.2 -999.0 15 9.0

0.5 3.2 1.3 2.5 11.2 7.7 -999.0 -999.00 1.3 0.4 -999.0 15 9.0

0.3 5.1 1.3 3.9 9.3 7.7 -999.0 -999.00 9.6 1.9 -999.0 15 9.0

0.3 11.4 1.3 8.8 3.0 7.7 -999.0 -999.00 3.3 0.3 -999.0 15 9.0

1.0 2.5 1.3 1.9 10.8 7.7 -999.0 -999.00 1.5 0.6 -999.0 15 9.0

0.3 2.2 1.3 1.7 12.2 7.7 -999.0 -999.00 2.5 1.1 2.5 15 9.0

0.3 0.0 1.3 0.0 14.4 7.7 -999.0 -999.00 4.7 -999.0 -999.0 15 9.0

0.3 0.0 1.3 0.0 14.4 7.7 -999.0 -999.00 4.7 -999.0 -999.0 15 9.0

0.6 5.1 1.3 3.9 -999.0 7.7 -999.0 -999.00 9.3 1.8 -999.0 -999.0 9.0

0.3 1.6 1.3 1.2 7.8 7.7 1.0 1.21 3.1 1.9 -999.0 5 9.0

-999.0 5.1 1.3 3.9 9.9 7.7 -999.0 -999.00 9.9 1.9 -999.0 15 9.0

0.3 3.8 1.3 2.9 10.6 7.7 -999.0 -999.00 0.9 0.2 -999.0 15 9.0

0.3 5.1 1.3 3.9 9.6 7.7 -999.0 -999.00 9.6 1.9 -999.0 15 9.0

0.2 6.4 1.3 4.9 -999.0 7.7 -999.0 -999.00 8.4 1.3 -999.0 15 9.0

0.3 5.1 1.3 3.9 -999.0 7.7 -999.0 -999.00 9.6 1.9 -999.0 -999.0 9.0

0.3 5.1 1.3 3.9 -999.0 7.7 -999.0 -999.00 9.6 1.9 -999.0 15 9.0

0.3 5.1 1.3 3.9 9.3 7.7 -999.0 -999.00 9.6 1.9 -999.0 15 9.0

0.3 2.5 1.3 1.9 11.9 7.7 -999.0 -999.00 1.3 0.5 -999.0 15 9.0

0.3 3.8 1.3 2.9 0.0 7.7 0.0 -999.00 -999.0 -999.0 -999.0 5 9.0

1.0 2.5 1.3 1.9 12.2 7.7 -999.0 -999.00 1.5 0.6 -999.0 15 9.0

0.2 5.1 1.3 3.9 9.3 7.7 -999.0 -999.00 9.7 1.9 -999.0 15 9.0

0.3 2.5 1.3 1.9 11.9 7.7 -999.0 -999.00 2.2 0.9 -999.0 15 9.0

0.3 1.6 1.3 1.2 -999.0 7.7 -999.0 -999.00 3.1 1.9 -999.0 15 9.0

0.3 2.9 1.3 2.2 11.5 7.7 -999.0 -999.00 1.8 0.6 -999.0 15 9.0

0.3 3.8 1.3 2.9 10.6 7.7 -999.0 -999.00 0.9 0.2 -999.0 15 9.0

0.5 0.0 1.3 0.0 14.4 7.7 -999.0 -999.00 4.5 -999.0 -999.0 15 9.0

0.3 2.5 1.3 1.9 11.9 7.7 -999.0 -999.00 2.2 0.9 2.2 15 9.0

0.3 1.3 1.3 1.0 -999.0 7.7 -999.0 -999.00 3.4 2.6 -999.0 -999.0 9.0

0.3 0.6 1.3 0.5 14.4 7.7 -999.0 -999.00 4.1 6.8 -999.0 15 9.0

0.3 1.3 1.3 1.0 -999.0 7.7 -999.0 -999.00 3.4 2.6 -999.0 -999.0 9.0

8
Appendix 1. Table A. Data 

SAMP_NO

BL9339

BL9345

BL9346

BL9347

BL9353

BL9354

BL9355

BL9360

BL9369

BL9370

BL9371

C93235

C93236

C93243

C93244

C93249

C93250

C93256

C93273

C93280

C93281

C93288

C93296

C93307

H934.2

L93118

L93119

L93121

L93128

L93135

L93137

L93154

L93156

L93162

M93104

M93106

M93107

M93108

M93109

PBR_CM_10Y PBR_PB AA_PB BA_PB PB_AABA JBA_PB BA1_PB PBAA_BA1 SAMP_NO

1.7 3567 4500 -999 -999.00 3200 -999 -999.00 BL9339

1.7 3950 2800 -999 -999.00 3300 -999 -999.00 BL9345

1.7 3933 4000 -999 -999.00 4000 -999 -999.00 BL9346

1.7 1600 790 -999 -999.00 1600 -999 -999.00 BL9347

-999.0 -999 1400 -999 -999.00 2900 -999 -999.00 BL9353

1.7 3433 3500 -999 -999.00 3400 -999 -999.00 BL9354

1.7 4550 2800 -999 -999.00 3700 -999 -999.00 BL9355

-999.0 -999 210 356 0.59 375 -999 -999.00 BL9360

0.6 -999 2100 2900 1.19 2900 -999 0.72 BL9369

1.7 3633 2300 -999 -999.00 3500 -999 0.66 BL9370

1.7 3300 2400 -999 -999.00 3300 -999 0.73 BL9371

1.7 2767 2300 -999 -999.00 3000 -999 -999.00 C93235

1.7 2267 1800 -999 -999.00 2500 -999 0.72 C93236

1.7 3325 2750 -999 -999.00 2200 -999 1.25 C93243

1.7 2533 1700 -999 -999.00 1900 1900 0.89 C93244

1.7 6775 -999 -999 -999.00 4900 -999 -999.00 C93249

1.7 6675 -999 -999 -999.00 3300 -999 -999.00 C93250

-999.0 -999 74 66 1.12 66 -999 -999.00 C93256

0.6 -999 1800 1200 1.50 1200 -999 -999.00 C93273

1.7 4833 2500 -999 -999.00 6000 -999 -999.00 C93280

1.7 3300 2200 -999 -999.00 3400 -999 0.65 C93281

1.7 1300 965 -999 -999.00 1300 -999 -999.00 C93288

-999.0 -999 110 110 1.00 110 -999 -999.00 C93296

-999.0 -999 185 555 0.33 555 -999 -999.00 C93307

-999.0 3800 3500 -999 -999.00 3900 -999 -999.00 H934.2

1.7 3933 4000 -999 -999.00 3900 -999 -999.00 L93118

1.7 1583 1900 -999 -999.00 2000 -999 0.95 L93119

0.6 -999 1100 775 1.42 775 -999 1.42 L93121

1.7 3883 4400 -999 -999.00 2900 -999 1.52 L93128

1.7 3767 4100 -999 -999.00 3600 -999 -999.00 L93135

1.7 4650 4200 -999 -999.00 4100 4100 1.02 L93137

-999.0 915 715 940 0.76 990 -999 -999.00 L93154

1.7 4167 4000 -999 -999.00 3200 -999 1.25 L93156

1.7 4150 3600 -999 -999.00 3300 -999 1.09 L93162

1.7 4100 -999 -999 -999.00 3300 -999 -999.00 M93104

1.7 3767 3600 -999 -999.00 3000 3000 1.20 M93106

-999.0 -999 165 211 0.78 320 -999 -999.00 M93107

1.7 1617 1600 -999 -999.00 2100 -999 -999.00 M93108

-999.0 -999 220 144 1.53 240 -999 -999.00 M93109

9
Appendix 1. Table A. Data 

SAMP_NO DATA_SET REF UTM_E UTM_N SYS ENV SEG SEC AAMTD ASSAY_INT M_TO_R FLUV_FTR

M9378 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 528694 5257714 P FB La p msr in 0-5aaba, 5-15 99 lat marsh

M9394 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 531194 5256615 Llt FB Mc p msr in 0-5aaba, 5-15 1647 lat lk littoral

M9395 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 531083 5257630 U LV La p msr in 0-5aaba, 5-15 669 distrib lv

M9396 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 530536 5258183 RU LV La p msr in 0-5aaba, 5-15 0 outside bnk

M9397 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 530829 5258681 RU LV Mc f msr in 0-5aaba, 5-15 18 outside bnk

RL93161 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 538090 5264836 RU LV Ma p msr in 0-5aaba, 5-15 1 outside bnk

RL93171 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 538948 5264429 U LV Ma p msr in 0-5aaba, 5-15 8 outside rlv

RL93177 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 539261 5265299 U LV Ma p msr in 0-5aaba, 5-15 667 distrib lv

RL93178 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 539405 5265123 U LV Ma p msr in 0-5aaba, 5-15 437 distrib lv

RL93193 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 541398 5264301 U LV Uc p msr in 0-5aaba, 5-15 56 straight rlv

RL93198 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 542194 5264121 RU LV Uc p msr in 0-5aaba, 5-15 2 inside bnk

RL93206 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 543680 5267131 P FB Uc loPb msr in 0-5aaba, 5-15 1450 lat marsh

RL93207 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 544275 5265402 RU LV Uc p msr in 0-5aaba, 5-15 35 inside bnk

RL93213 USGS/WRD/93 Fousek (1996), Fousek (unpub data, 1993) 544778 5265252 RU LV Uc p msr in 0-5aaba, 5-15 0 straight bnk

10
Appendix 1. Table A. Data 

SAMP_NO

M9378

M9394

M9395

M9396

M9397

RL93161

RL93171

RL93177

RL93178

RL93193

RL93198

RL93206

RL93207

RL93213

ASH_CM AA_CM AA_10Y AA_CM_10Y BA_CM BA_10Y BA_CM_10Y SR_AABA JBA_CM JBA_AA BA1_CM PBR_CM PBR_10Y

0.3 2.5 1.3 1.0 9.2 7.7 -999.0 -999.00 2.2 0.9 2.2 15 9.0

2.5 3.8 1.3 2.9 11.2 7.7 -999.0 -999.00 8.7 2.3 -999.0 15 9.0

0.3 4.5 1.3 3.4 10.3 7.7 -999.0 -999.00 0.2 0.0 -999.0 15 9.0

0.2 2.5 1.3 1.9 11.9 7.7 -999.0 -999.00 2.3 0.9 -999.0 15 9.0

0.3 2.5 1.3 1.9 6.9 7.7 0.9 2.13 2.2 0.9 -999.0 5 9.0

0.3 2.2 1.3 1.7 12.5 7.7 -999.0 -999.00 2.5 1.1 -999.0 15 9.0

-999.0 -999.0 1.3 1.9 11.9 7.7 -999.0 -999.00 -999.0 -999.0 -999.0 15 9.0

0.3 1.0 1.3 0.8 13.4 7.7 -999.0 -999.00 3.7 3.7 -999.0 15 9.0

0.3 1.6 1.3 1.2 13.1 7.7 -999.0 -999.00 3.1 1.9 -999.0 15 9.0

0.2 2.5 1.3 1.9 12.2 7.7 -999.0 -999.00 2.3 0.9 -999.0 15 9.0

0.2 2.2 1.3 1.7 12.2 7.7 -999.0 -999.00 2.6 1.2 -999.0 15 9.0

0.5 1.6 1.3 1.2 -999.0 7.7 -999.0 -999.00 2.9 1.8 -999.0 -999.0 9.0

0.3 1.9 1.3 1.5 12.5 7.7 -999.0 -999.00 2.8 1.5 -999.0 15 9.0

0.3 1.6 1.3 1.2 13.4 7.7 -999.0 -999.00 3.1 1.9 -999.0 15 9.0

11
Appendix 1. Table A. Data 

SAMP_NO

M9378

M9394

M9395

M9396

M9397

RL93161

RL93171

RL93177

RL93178

RL93193

RL93198

RL93206

RL93207

RL93213

PBR_CM_10Y PBR_PB AA_PB BA_PB PB_AABA JBA_PB BA1_PB PBAA_BA1 SAMP_NO

1.7 3167 2600 -999 -999.00 2800 2800 0.93 M9378

1.7 2767 1300 -999 -999.00 620 -999 -999.00 M9394

1.7 3800 2100 -999 -999.00 3500 -999 0.60 M9395

1.7 3300 3650 -999 -999.00 2550 2550 1.43 M9396

0.6 -999 1800 1500 1.20 1500 1500 1.20 M9397

1.7 4533 4100 -999 -999.00 4700 4700 -999.00 RL93161

1.7 4675 5500 -999 -999.00 6000 -999 -999.00 RL93171

1.7 2700 850 -999 -999.00 -999 -999 -999.00 RL93177

1.7 5800 6600 -999 -999.00 -999 -999 -999.00 RL93178

1.7 6417 6000 -999 -999.00 6100 6100 0.98 RL93193

1.7 6792 5150 -999 -999.00 5400 -999 -999.00 RL93198

-999.0 -999 330 628 0.53 260 -999 -999.00 RL93206

1.7 3267 2400 -999 -999.00 3600 -999 -999.00 RL93207

1.7 2567 2100 -999 -999.00 2900 -999 -999.00 RL93213

12
cda_sr_pb-of_meta.txt

Identification_Information:

 Citation:

 Citation_Information:

 Originator: Bookstrom, A.A.

 Originator: Box, S.E.

 Originator: Fousek, R.S.

 Originator: Jackson, B.L.

 Originator: Wallis, J.C.

 Originator: Kayser, H.Z.

 Publication_Date: 2004

 Title: Spatial database in Baseline and Historic Depositional Rates and Lead 

Concentrations, Floodplain Sediments, Lower Coeur d'Alene River, Idaho

 Geospatial_Data_Presentation_Form: vector digital data

 Series_Information:

 Series_Name: U.S. Geological Survey Open-File Report

 Issue_Identification: 04-1211

 Online_Linkage: http://pubs.usgs.gov/of/2004-1211

 Description:

 Abstract:

 Lead-rich sediments, containing at least 1,000 ppm of lead cover about 60 km2 

of the 84-km2 floor of the main stem of the Coeur d'Alene River valley (Bookstrom 

and others, 2001). Large-scale mining and milling of veins enriched in silver (Ag), 

lead (Pb), zinc (Zn), and other metals began in 1886 in the Coeur d'Alene mining 

region. Until 1968, some mills discarded pulverized tailings, containing particulate

metallic-sulfide minerals, directly into streams of the upper Coeur d'Alene River 

drainage basin. The discarded tailings washed down-stream, mixed with other 

sediments in transport, and were re-deposited down-valley.

 Frequent floods continue to transport metal-enriched sediment down-valley and 

onto the floodplain. Thick deposits of lead-rich sediments are present in the 

low-gradient river channel west of Cataldo Landing. These river-channel deposits of 

lead-rich sediments are an important secondary source of lead-rich sediments, 

vulnerable to transport during floods. Floodwaters continue to mobilize and 

re-deposit lead-rich sediments from this large secondary source, even though 

tailings have not been discarded into tributary streams since 1968, and large 

volumes of lead-rich sediments were removed from tributary streams and floodplains 

during the late 1990's. Furthermore, floodwaters will continue to remobilize 

lead-rich sediments from the river channel, as well as from smaller secondary 

sources along its banks and levees, and will continue to deposit lead-rich sediments

in lateral flood basins, where waterfowl commonly feed, until these secondary 

sources are removed, stabilized and covered, or effectively separated from the flood

basins.

 The "May 1980 Mt. St. Helens volcanic-ash layer" provided an excellent 1980 

time-stratigraphic marker layer, referred to as the"1980 volcanic-ash layer". The 

pre-remedial baseline interval is defined as sediment above the 1980 

time-stratigraphic horizon at the time of measurement and sampling, most of which 

was done between 1991 and 1995 (1993 +/- 2y), and all of which was done between 1990

and 1998.

 Purpose: The primary purpose of this study is to quantify pre-remedial baseline 

depositional rates and lead concentrations in sediments deposited between 1980 and 

about 1993, in various settings on the floodplain of the main stem of the Coeur 

d'Alene River, and compare baseline to historic and background depositional rates 

and lead concentrations. The secondary purpose is to explain the implications of 

this information for environmental remediation in the context of fluvial processes 

still acting on secondary sources of lead-rich sediments, previously deposited along

floodwater flow paths. The CDA_SR_PB spatial database was created to enable the 

authors to display sample sites, showing baseline sediment deposition rates, and 

lead concentrations in baseline-interval sediments, in the context of surficial 

geologic units, mapped on the floodplain of the main stem of the Coeur d'Alene 

River. This information was gathered and organized in support of ongoing studies of 

the environmental impacts of lead-rich floodplain sediments, and long-term cleanup 

plans being formulated by the U.S. Environmental Protection Agency and others.

 Supplemental_Information: The CDA_SR_PB spatial dataset is an ESRI-formatted 

shapefile (that consists of a collection of files of the same name having the 

Page 1
cda_sr_pb-of_meta.txt

following file extensions: DBF, SBN, SBX, SHP, and SHX). It is not merely a new 

"revision" of the pre-existing data (Bookstrom and others, 2001) from which it was 

built: the addition of one sample site, the deletion of a few others, and a 

significant amount of new sedimentation-rate data make it a new product. The 

dataset contains information for 131 sample localities.

 Time_Period_of_Content:

 Time_Period_Information:

 Single_Date/Time:

 Calendar_Date: 2004

 Currentness_Reference: publication date

 Status:

 Progress: Complete for informal Open-File Report publication; however, minor 

revisions are likely to be made to the spatial database when the report is 

superseded by a U.S. Geological Survey Scientific Investigations Report.

 Maintenance_and_Update_Frequency: Minor revisions may likely be made to the 

spatial database when it is formally published as a U.S. Geological Survey 

Scientific Investigations Report.

 Spatial_Domain:

 Bounding_Coordinates:

 West_Bounding_Coordinate: -116.820096

 East_Bounding_Coordinate: -116.252574

 North_Bounding_Coordinate: 47.585365

 South_Bounding_Coordinate: 47.340604

 Keywords:

 Theme:

 Theme_Keyword_Thesaurus: Glossary of Geology, American Geological Institute

 Theme_Keyword: Surficial geology

 Theme_Keyword: Lead

 Theme_Keyword: Tailings

 Theme_Keyword: Sediment

 Theme_Keyword: Sedimentation rate

 Place:

 Place_Keyword: Coeur d'Alene River

 Place_Keyword: Kootenai County

 Place_Keyword: Shoshone County

 Place_Keyword: Idaho

 Place_Keyword: Pacific Northwest

 Place_Keyword: United States

 Place_Keyword: USA

 Access_Constraints: none

 Use_Constraints: Any hardcopies utilizing these data sets shall clearly indicate 

their source. If the users have modified the data in any way they are obligated to 

describe the type of modifications they have performed. User specifically agrees not

to misrepresent these data sets, nor to imply that changes they made were approved 

by the U.S. Geological Survey.

 Point_of_Contact:

 Contact_Information:

 Contact_Person_Primary:

 Contact_Person: Arthur A. Bookstrom

 Contact_Organization: U.S. Geological Survey

 Contact_Position: Geologist

 Contact_Address:

 Address_Type: mailing and physical address

 Address: 904 W. Riverside Avenue, Rm. 202

 City: Spokane

 State_or_Province: Washington

 Postal_Code: 99201

 Country: USA

 Contact_Voice_Telephone: 1-509-368-3119

 Contact_Facsimile_Telephone: 1-509-368-3199

 Contact_Electronic_Mail_Address: abookstrom@usgs.gov

 Data_Set_Credit: John C. Wallis and Helen Z. Kayser (contractors) wrote the 

metadata, and Gary L. Raines reviewed the digital data and metadata.

Page 2
cda_sr_pb-of_meta.txt

 Security_Information:

 Security_Classification_System: none

 Security_Classification: Unclassified

 Native_Data_Set_Environment: Microsoft Windows 2000 Version 5.0 (Build 2195) 

Service Pack 4; ESRI ArcCatalog 9.0.0.535

Data_Quality_Information:

 Attribute_Accuracy:

 Attribute_Accuracy_Report: Accuracy was verified by manual comparison of the 

source data with hardcopy printouts, and on screen evaluations.

 Logical_Consistency_Report: These data are believed to be logically consistent, 

though no tests were performed other than using the data for analysis.

 Completeness_Report: Original vector data was assumed to be complete.

 Positional_Accuracy:

 Horizontal_Positional_Accuracy:

 Horizontal_Positional_Accuracy_Report: The horizontal positional accuracy for 

the digital data is no better than about 15 meters based on digitizing RMS error.

 Quantitative_Horizontal_Positional_Accuracy_Assessment:

 Horizontal_Positional_Accuracy_Value: 15 meters

 Vertical_Positional_Accuracy:

 Vertical_Positional_Accuracy_Report: No vertical data.

 Lineage:

 Source_Information:

 Source_Citation:

 Citation_Information:

 Originator: Bookstrom, A.A.

 Originator: Box, S.E.

 Originator: Campbell, J.K.

 Originator: Foster, K.I.

 Originator: Jackson, B.L.

 Publication_Date: 2001

 Title: Lead rich sediments, Coeur d'Alene River valley, Idaho: Area, 

volume, tonnage, and lead content

 Edition: 1.0

 Geospatial_Data_Presentation_Form: digital map

 Series_Information:

 Series_Name: Open-File Report

 Issue_Identification: 01-140

 Publication_Information:

 Publication_Place: Menlo Park, CA

 Publisher: U.S. Geological Survey

 Online_Linkage: http://geopubs.wr.usgs.gov/open-file/of01-140/

 Source_Scale_Denominator: 24000

 Type_of_Source_Media: map

 Source_Time_Period_of_Content:

 Time_Period_Information:

 Single_Date/Time:

 Calendar_Date: 2001

 Source_Currentness_Reference: publication date

 Source_Citation_Abbreviation: Bookstrom and others (2001)

 Source_Contribution: Two dBase4 files (ALSAMPB.DBF and THXPB11.DBF) provided 

sample site locations. ESRI shape files (CDASURF4_UTM.SHP, FPAREAM2.SHP, 

SEGMENTS.SHP and PB1000.SHP) were incorporated into the accompanying map plates to 

provide a basemap on which to overlay data from the CDA_SR_PB spatial database.

 Source_Information:

 Source_Citation:

 Citation_Information:

 Originator: Horowitz, A.J.

 Originator: Erlick, K.A.

 Originator: Robbins, J.A.

 Originator: Cook, R.B.

 Publication_Date: 1995

 Title: Effect of mining and related activities on the sediment

 Edition: 1.0

Page 3
cda_sr_pb-of_meta.txt

 Geospatial_Data_Presentation_Form: tabular digital data

 Publication_Information:

 Publication_Place: New York, New York

 Publisher: John Wiley and Sons, LTD

 Type_of_Source_Media: GPS Receiver

 Source_Time_Period_of_Content:

 Time_Period_Information:

 Single_Date/Time:

 Calendar_Date: 1995

 Source_Currentness_Reference: publication date

 Source_Citation_Abbreviation: Horowitz and others (1995)

 Source_Contribution: One sample point from this tabular report was added to 

the CDA_SR_PB dataset. The sample point location was obtained by a GPS receiver.

 Process_Step:

 Process_Description: A new sample point location (from Horowitz and others, 

1995), and new data on sedimentation rate and lead concentration were added to the 

dBase4 file (Bookstrom and others, 2001) using Microsoft Excel. The dBase4 file was

then imported into ArcView and converted to a shape file CDA_SR_PB. An ArcView 

legend file, CDA_SR_PB.AVL, was made to format the theme.

 Process_Date: Unknown

 Process_Step:

 Process_Description: The CDASURF4_UTM, FPAREAM2, SEGMENTS and PB1000 

shapefiles (Bookstrom and others, 2001) were imported into an ArcView project and 

used to provide a basemap on which sedimentation-rate and lead- concentration data 

could be shown. These data were used without modification with the exception of 

subsetting the SEGMENTS shapefile (to exclude valley boundary lines numbered 1 

through 8, due to their irrelevance in this study.

 Source_Used_Citation_Abbreviation: Bookstrom and others (2001), Horowitz and 

others (1995)

 Process_Date: 2001 - 2005

 Process_Contact:

 Contact_Information:

 Contact_Person_Primary:

 Contact_Person: Arthur A. Bookstrom

 Contact_Organization: U.S. Geological Survey

 Contact_Position: Geologist

 Contact_Address:

 Address_Type: mailing and physical address

 Address: 904 W. Riverside Avenue, Rm. 202

 City: Spokane

 State_or_Province: WA

 Postal_Code: 99201

 Country: USA

 Contact_Voice_Telephone: 1-509-368-3119

 Contact_Facsimile_Telephone: 1-509-368-3199

 Contact_Electronic_Mail_Address: abookstrom@usgs.gov

 Process_Step:

 Process_Description: Metadata imported.

 Source_Used_Citation_Abbreviation: 

C:\WRDIA\CDA_meta\6th_time_Jan05\2_OFR\metadata\cda_sr_pb-meta.xml

Spatial_Data_Organization_Information:

 Direct_Spatial_Reference_Method: Vector

 Point_and_Vector_Object_Information:

 SDTS_Terms_Description:

 SDTS_Point_and_Vector_Object_Type: Entity point

 Point_and_Vector_Object_Count: 131

Spatial_Reference_Information:

 Horizontal_Coordinate_System_Definition:

 Planar:

 Grid_Coordinate_System:

 Grid_Coordinate_System_Name: Universal Transverse Mercator

 Universal_Transverse_Mercator:

 UTM_Zone_Number: 11

Page 4
cda_sr_pb-of_meta.txt

 Transverse_Mercator:

 Scale_Factor_at_Central_Meridian: 0.999600

 Longitude_of_Central_Meridian: -117.000000

 Latitude_of_Projection_Origin: 0.000000

 False_Easting: 500000.000000

 False_Northing: 0.000000

 Planar_Coordinate_Information:

 Planar_Coordinate_Encoding_Method: coordinate pair

 Coordinate_Representation:

 Abscissa_Resolution: 0.000064

 Ordinate_Resolution: 0.000064

 Planar_Distance_Units: meters

 Geodetic_Model:

 Horizontal_Datum_Name: North American Datum of 1927

 Ellipsoid_Name: Clarke 1866

 Semi-major_Axis: 6378206.400000

 Denominator_of_Flattening_Ratio: 294.978698

Entity_and_Attribute_Information:

 Detailed_Description:

 Entity_Type:

 Entity_Type_Label: cda_sr_pb

 Entity_Type_Definition: ESRI point shapefile (which contains files with the 

extensions .SHP, .SHX, .SBX, .SBN, .DBF) of sedimentation rates and lead 

concentrations for 131 location points in the study area.

 Attribute:

 Attribute_Label: FID

 Attribute_Definition: Internal feature number.

 Attribute_Definition_Source: ESRI

 Attribute_Domain_Values:

 Unrepresentable_Domain: Sequential unique whole numbers that are 

automatically generated.

 Attribute:

 Attribute_Label: Shape

 Attribute_Definition: Feature geometry.

 Attribute_Definition_Source: ESRI

 Attribute_Domain_Values:

 Unrepresentable_Domain: Coordinates defining the features.

 Attribute:

 Attribute_Label: SAMP_NO

 Attribute_Definition: SAMPLE NUMBER - from original study (see Bookstrom and 

others, 2001)

 Attribute_Domain_Values:

 Attribute:

 Attribute_Label: DATA_SET

 Attribute_Definition: DATA-SET IDENTIFIER - It consists of initials 

researcher's affiliation, researcher's last name, and year that data were collected.

 Attribute_Domain_Values:

 Attribute:

 Attribute_Label: REF

 Attribute_Definition: REFERENCE IDENTIFIER - The data source citation. 

Complete references are provided in the report text in the List of References 

section.

 Attribute:

 Attribute_Label: UTM_E

 Attribute_Definition: UTM EAST - The coordinate (in meters) of sample site, 

(UTM map projection: Universal Transverse Mercator, zone 11, North American Datum of

1927)

 Attribute:

 Attribute_Label: UTM_N

 Attribute_Definition: UTM NORTH - The coordinate (in meters) of sample site, 

(UTM map projection: Universal Transverse Mercator, zone 11, North American Datum of

1927)

 Attribute:

Page 5
cda_sr_pb-of_meta.txt

 Attribute_Label: SYS

 Attribute_Definition: SYSTEM IDENTIFIER - The label used to identify wetland 

system

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: RU

 Enumerated_Domain_Value_Definition: River bank Upland - wedge shaped 

deposits of lead-rich sediments on the river-facing slope of the natural levee

 Enumerated_Domain:

 Enumerated_Domain_Value: U

 Enumerated_Domain_Value_Definition: (Levee/) Upland - Floodplain-facing 

slope of the natural levee, from the levee crest to the adjacent lateral marsh or 

lateral lake

 Enumerated_Domain:

 Enumerated_Domain_Value: P

 Enumerated_Domain_Value_Definition: Palustrine - lateral marshes, 

seasonally to perinnally flooded to less than 2 meters deep

 Enumerated_Domain:

 Enumerated_Domain_Value: L

 Enumerated_Domain_Value_Definition: Lacustrine - lateral lakes, wetlands, 

and deepwater habitats

 Enumerated_Domain:

 Enumerated_Domain_Value: Ldd

 Enumerated_Domain_Value_Definition: a distributary delta in a Lacustrine 

environment

 Enumerated_Domain:

 Enumerated_Domain_Value: Llt

 Enumerated_Domain_Value_Definition: Lacustrine, littoral - a subset of the

Lacustrine system, wetlands and deepwater habitats less than 2 meters deep (margins)

at summer water level

 Enumerated_Domain:

 Enumerated_Domain_Value: Llm

 Enumerated_Domain_Value_Definition: Lacustrine, limnetic - a subset of the

Lacustrine system, wetlands and deepwater habitats more than 2m deep (bottoms) at 

summer water level

 Enumerated_Domain:

 Enumerated_Domain_Value: A

 Enumerated_Domain_Value_Definition: Anthropogenic - man-made features 

(includes roads, railroad embankments, and dredge-spoil deposits)

 Enumerated_Domain:

 Enumerated_Domain_Value: DLT

 Enumerated_Domain_Value_Definition: Coeur d'Alene River delta - the area 

from the mouth of the river to floor of the lake

 Enumerated_Domain:

 Enumerated_Domain_Value: UA

 Enumerated_Domain_Value_Definition: Upland Anthropogenic - artificial 

features above summer water level

 Enumerated_Domain:

 Enumerated_Domain_Value: PA

 Enumerated_Domain_Value_Definition: Palustrine Anthropogenic - artificial 

features within the wetlands

 Attribute:

 Attribute_Label: ENV

 Attribute_Definition: ENVIRONMENT IDENTIFIER - The label used to identify 

sedimentary floodplain environment

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: LV

 Enumerated_Domain_Value_Definition: Levee - man-made embankment to prevent

flooding

 Enumerated_Domain:

 Enumerated_Domain_Value: FB

 Enumerated_Domain_Value_Definition: Flood basin - an area of the earth 

Page 6
cda_sr_pb-of_meta.txt

which holds water at times of floods due to the strata dip usually from the sides 

toward the middle (the river)

 Attribute:

 Attribute_Label: SEG

 Attribute_Definition: SEGMENT IDENTIFIER - The label used to identify a 

segment of the river valley

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: Ua

 Enumerated_Domain_Value_Definition: Kingston segment (located in the upper

part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Ub

 Enumerated_Domain_Value_Definition: Cataldo segment (located in the upper 

part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Uc

 Enumerated_Domain_Value_Definition: Dudley segment (located in the upper 

part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Ma

 Enumerated_Domain_Value_Definition: Rose Lake segment (located in the 

middle part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Mb

 Enumerated_Domain_Value_Definition: Lane segment (located in the middle 

part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Mc

 Enumerated_Domain_Value_Definition: Killarney segment (located in the 

middle part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: La

 Enumerated_Domain_Value_Definition: Medimont segment (located in the lower

part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Lb

 Enumerated_Domain_Value_Definition: Blue Lake segment (located in the 

lower part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: Lc

 Enumerated_Domain_Value_Definition: Harrison segment (located in the lower

part of the main stem of the Coeur d'Alene River valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: DLTT

 Enumerated_Domain_Value_Definition: Coeur d'Alene River delta toe segment 

(located in the Coeur d'Alene Lake)

 Enumerated_Domain:

 Enumerated_Domain_Value: NF

 Enumerated_Domain_Value_Definition: North Fork segment (located in the 

North Fork of the Coeur d'Alene River Valley)

 Enumerated_Domain:

 Enumerated_Domain_Value: SJRV

 Enumerated_Domain_Value_Definition: St. Joe segment (located in the St. 

Joe River valley)

 Attribute:

 Attribute_Label: SEC

 Attribute_Definition: SECTION IDENTIFIER - Descriptions of completeness of the

stratigraphic section of mining-era sediments

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: f

 Enumerated_Domain_Value_Definition: Full stratigraphic section (includes 

Page 7
cda_sr_pb-of_meta.txt

1980 ash layer)

 Enumerated_Domain:

 Enumerated_Domain_Value: fna

 Enumerated_Domain_Value_Definition: Full stratigraphic section (does NOT 

include 1980 ash layer)

 Enumerated_Domain:

 Enumerated_Domain_Value: nfna

 Enumerated_Domain_Value_Definition: Nearly full stratigraphic section 

(does NOT include 1980 ash layer)

 Enumerated_Domain:

 Enumerated_Domain_Value: p

 Enumerated_Domain_Value_Definition: Partial stratigraphic section 

(includes 1980 ash layer and bottoms in lead-rich sediments)

 Enumerated_Domain:

 Enumerated_Domain_Value: loPb

 Enumerated_Domain_Value_Definition: Stratigraphic section with less than 

1000 ppm of lead in sediments above and below the 1980 ash layer

 Attribute:

 Attribute_Label: AAMTD

 Attribute_Definition: AA METHOD - the method used to identify and measure 

thickness of post-1980 sediments

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: msr cm

 Enumerated_Domain_Value_Definition: Thickness above 1980 ash layer, 

measured in centimeters

 Enumerated_Domain:

 Enumerated_Domain_Value: msr in

 Enumerated_Domain_Value_Definition: Thickness above 1980 ash layer, 

measured in inches

 Enumerated_Domain:

 Enumerated_Domain_Value: Cs isotp

 Enumerated_Domain_Value_Definition: Thickness in centimeters of sediment 

deposited after about 1980 (half of the thickness of the sediment deposited after 

1969), as indicated by Cesium isotopic dating of the contact between silty 

lamentated sediment and overlying non-layered sediment in freeze box core M92CS.

 Enumerated_Domain:

 Enumerated_Domain_Value: correl

 Enumerated_Domain_Value_Definition: Thickness in centimeters of sediment 

deposited after about 1980 (half of the thickness of the sediment deposited after 

1969), as indicated by correlation of the contact between silty lamentated sediment 

and overlying non-layered sediment, as dated by correlation with freeze box core 

M92CS in which the 1969 contact was dated by the Cesium isotopic method.

 Enumerated_Domain:

 Enumerated_Domain_Value: nd

 Enumerated_Domain_Value_Definition: Thickness was not determined

 Attribute:

 Attribute_Label: ASSAY_INT

 Attribute_Definition: ASSAY INTERVAL - The sample-assay depth-interval 

criteria

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: 2 span

 Enumerated_Domain_Value_Definition: Samples were taken in a continuous 

series of 2-cm thick intervals.

 Enumerated_Domain:

 Enumerated_Domain_Value: 1-2.5 span

 Enumerated_Domain_Value_Definition: Samples were taken in a continuous 

series of 1- to 2.5-cm thick intervals.

 Enumerated_Domain:

 Enumerated_Domain_Value: 0-5 aaba, 5-15

 Enumerated_Domain_Value_Definition: Sample intervals were chosen by the 

following criteria: a 0-5 cm interval (split into above-ash and below-ash parts) and

Page 8
cda_sr_pb-of_meta.txt

a 5-15 cm interval

 Enumerated_Domain:

 Enumerated_Domain_Value: strat span

 Enumerated_Domain_Value_Definition: Continuous samples represent variable 

depth spans, based on stratigraphic layering

 Enumerated_Domain:

 Enumerated_Domain_Value: strat spot

 Enumerated_Domain_Value_Definition: Discontinuous spot samples taken from 

the midpoint of the stratigraphic interval represented+

 Enumerated_Domain:

 Enumerated_Domain_Value: aatp, ba1btm

 Enumerated_Domain_Value_Definition: Spot samples were collected at top of 

AA interval, at bottom of BA1 interval, and at variable depth intervals below the 

BA1 interval.

 Enumerated_Domain:

 Enumerated_Domain_Value: na

 Enumerated_Domain_Value_Definition: Sample was collected but not analyzed 

for lead.

 Enumerated_Domain:

 Enumerated_Domain_Value: intrvl>aa

 Enumerated_Domain_Value_Definition: Recorded thickness of sampling 

interval includes but exceeds thickness of sediments above the 1980 ash layer. This 

information was not used in this study.

 Attribute:

 Attribute_Label: M_TO_R

 Attribute_Definition: METERS to RIVER - The distance (measured in meters) from

sample site to the nearest riverbank

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 2373

 Attribute_Units_of_Measure: meters

 Attribute:

 Attribute_Label: FLUV_FTR

 Attribute_Definition: FLUVIAL FEATURE - the type of feature found at sample 

site

 Attribute_Domain_Values:

 Enumerated_Domain:

 Enumerated_Domain_Value: alluv terrace

 Enumerated_Domain_Value_Definition: alluvial terrace

 Enumerated_Domain:

 Enumerated_Domain_Value: distrib lv

 Enumerated_Domain_Value_Definition: distributary levee

 Enumerated_Domain:

 Enumerated_Domain_Value: inside bnk

 Enumerated_Domain_Value_Definition: inside bank - inside margin of a river

channel on a curve, bend or meander

 Enumerated_Domain:

 Enumerated_Domain_Value: inside rlv

 Enumerated_Domain_Value_Definition: inside river levee - inside margin of 

a river levee on a curve, bend or meander

 Enumerated_Domain:

 Enumerated_Domain_Value: lat lk delta

 Enumerated_Domain_Value_Definition: lateral lake delta

 Enumerated_Domain:

 Enumerated_Domain_Value: lat lk limetic

 Enumerated_Domain_Value_Definition: lateral lake limnetic bottoms (in more

than 2 meters deep at summer water level)

 Enumerated_Domain:

 Enumerated_Domain_Value: lat lk littoral

 Enumerated_Domain_Value_Definition: lateral lake littoral margins (in less

than 2 meters deep at summer water level)

 Enumerated_Domain:

Page 9
cda_sr_pb-of_meta.txt

 Enumerated_Domain_Value: lat marsh

 Enumerated_Domain_Value_Definition: lateral marsh

 Enumerated_Domain:

 Enumerated_Domain_Value: main delta

 Enumerated_Domain_Value_Definition: main delta of the river

 Enumerated_Domain:

 Enumerated_Domain_Value: marsh anthr

 Enumerated_Domain_Value_Definition: anthropogenic marsh

 Enumerated_Domain:

 Enumerated_Domain_Value: n fk bank

 Enumerated_Domain_Value_Definition: bank of the North Fork River

 Enumerated_Domain:

 Enumerated_Domain_Value: outside bnk

 Enumerated_Domain_Value_Definition: outside bank - outside margin of a 

river channel on a curve, bend or meander

 Enumerated_Domain:

 Enumerated_Domain_Value: outside rlv

 Enumerated_Domain_Value_Definition: outside river levee - outside margin 

of a river levee on a curve, bend or meander

 Enumerated_Domain:

 Enumerated_Domain_Value: splay

 Enumerated_Domain_Value_Definition: sand splay

 Enumerated_Domain:

 Enumerated_Domain_Value: st joe bank

 Enumerated_Domain_Value_Definition: bank of the St. Joe River

 Enumerated_Domain:

 Enumerated_Domain_Value: straight bnk

 Enumerated_Domain_Value_Definition: straight bank - bank on a straight 

portion of the river channel

 Enumerated_Domain:

 Enumerated_Domain_Value: straight rlv

 Enumerated_Domain_Value_Definition: straight river levee - river levee 

along a straight portion of a river channel

 Enumerated_Domain:

 Enumerated_Domain_Value: uplnd anthr

 Enumerated_Domain_Value_Definition: anthropogenic upland

 Attribute:

 Attribute_Label: ASH_CM

 Attribute_Definition: ASH in CENTIMENTERS -Thickness (measured in centimeters)

of the 1980 volcanic-ash layer

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 4

 Attribute_Units_of_Measure: centimeters

 Attribute:

 Attribute_Label: AA_CM

 Attribute_Definition: AA in CENTIMETERS - Thickness (measured in centimeters) 

of sediments deposited above the 1980 volcanic-ash layer

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 40

 Attribute_Units_of_Measure: centimeters

 Attribute:

 Attribute_Label: AA_10Y

 Attribute_Definition: AA in 10 YEARS -Maximum time period (measured in decimal

decades) from May 1980 to the sampling date in which sediments could have been 

deposited subsequent to (above) the 1980 volcanic-ash layer

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 1

 Range_Domain_Maximum: 1.8

Page 10
cda_sr_pb-of_meta.txt

 Attribute_Units_of_Measure: decimal decades

 Attribute:

 Attribute_Label: AA_CM_10Y

 Attribute_Definition: AA in CENTIMETERS in 10 YEARS -Averaged rate of 

deposition (cm/decade) for sediments deposited subsequent to the 1980 volcanic-ash 

layer

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 28.6

 Attribute_Units_of_Measure: centimeters per decimal decade

 Attribute:

 Attribute_Label: BA_CM

 Attribute_Definition: BA in CENTIMETERS - Thickness (measured in centimeters) 

of lead-rich sediments (containing at least 1000 ppm of lead) deposited prior to 

(below) the 1980 volcanic-ash layer (and representing a time span from about 1903 to

1980)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 290

 Attribute_Units_of_Measure: centimeters

 Attribute:

 Attribute_Label: BA_10Y

 Attribute_Definition: BA in 10 YEARS - Maximum time period (measured in 

decimal decades from about 1903 and 1980) in which sediments could have been 

deposited prior to the 1980

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 2.9

 Range_Domain_Maximum: 7.7

 Attribute_Units_of_Measure: decimal decades

 Attribute:

 Attribute_Label: BA_CM_10Y

 Attribute_Definition: BA in CENTIMETERS in 10 YEARS - Averaged rate of 

deposition (cm/decade) for sediments deposited prior to the 1980 volcanic-ash layer.

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 35.5

 Attribute_Units_of_Measure: centimenters per decimal decades

 Attribute:

 Attribute_Label: SR_AABA

 Attribute_Definition: SEDIMENTATION RATE in AABA - Ratio of the sedimentation 

rate of sediments deposited after the May 1980 eruption of Mt. St. Helens to 

sediments deposited prior to the May 1980 eruption of Mt. St. Helens. (A value of 

-999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0.11

 Range_Domain_Maximum: 10.31

 Attribute_Units_of_Measure: ratio

 Attribute:

 Attribute_Label: JBA_CM

 Attribute_Definition: JBA in CENTIMETERS - Thickness (measured in 

centimeters) of sample interval just below the base of the 1980 volcanic-ash layer. 

(A value of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0.2

 Range_Domain_Maximum: 36

 Attribute_Units_of_Measure: centimeters

 Attribute:

Page 11
cda_sr_pb-of_meta.txt

 Attribute_Label: JBA_AA

 Attribute_Definition: Ratio of thickness of sample interval immediately below 

the base of the 1980 volcanic-ash layer to thickness of sediments overlying the 1980

volcanic-ash layer. (A value of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0

 Range_Domain_Maximum: 8.8

 Attribute_Units_of_Measure: ratio

 Attribute:

 Attribute_Label: BA1_CM

 Attribute_Definition: BA1 in CENTIMETERS - Thickness of stratigraphic interval

BA1, defined as a JBA interval with thickness equal to thickness of the overlying AA

interval +/- 10%. (BA1_CM therefore ranges from 0.9*AA_CM to 1.1*AA_CM in the same 

section). (A value of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 2.2

 Range_Domain_Maximum: 16

 Attribute_Units_of_Measure: centimeters

 Attribute:

 Attribute_Label: PBR_CM

 Attribute_Definition: PBR in CENTIMETERS - Composite thickness (measured in 

centimeters) of sampling intervals which contain lead-rich sediments with values at 

or exceeding 1,000 ppm Pb. (A value of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 5

 Range_Domain_Maximum: 300

 Attribute_Units_of_Measure: centimeters

 Attribute:

 Attribute_Label: PBR_10Y

 Attribute_Definition: PBR in 10 YEARS - Time period (measured in decimal 

decades) in which lead-rich sediments were deposited (PBR_10Y = sample date - 1903).

(A value of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 4.1

 Range_Domain_Maximum: 9.5

 Attribute_Units_of_Measure: decimal decades

 Attribute:

 Attribute_Label: PBR_CM_10Y

 Attribute_Definition: PBR in CENTIMETERS in 10 YEARS - Average sedimentation 

rate (cm/decade) for the composite thickness of sampling intervals which contain 

lead-rich sediments with values at or exceeding 1,000 ppm Pb. (A value of -999 

indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0.6

 Range_Domain_Maximum: 33

 Attribute_Units_of_Measure: cemtimeters per decimal decades

 Attribute:

 Attribute_Label: PBR_PB

 Attribute_Definition: PBR LEAD - Weighted-average concentration of lead 

(measured in ppm) for the composite thickness of sampling intervals which contain 

lead-rich sediments with values at or exceeding 1,000 ppm Pb. (A value of -999 

indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 915

 Range_Domain_Maximum: 14129

 Attribute_Units_of_Measure: ppm (parts per million)

 Attribute:

Page 12
cda_sr_pb-of_meta.txt

 Attribute_Label: AA_PB

 Attribute_Definition: AA LEAD - Weighted-average concentration of lead 

(measured in ppm) in sediments deposited above the 1980 volcanic-ash layer. (A value

of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 21

 Range_Domain_Maximum: 7460

 Attribute_Units_of_Measure: ppm (parts per million)

 Attribute:

 Attribute_Label: BA_PB

 Attribute_Definition: Weighted-average concentration of lead (ppm Pb) in 

sediments deposited below the 1980 volcanic-ash layer. (A value of -999 indicates no

data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 23

 Range_Domain_Maximum: 13940

 Attribute_Units_of_Measure: ppm (parts per million)

 Attribute:

 Attribute_Label: PB_AABA

 Attribute_Definition: Ratio of weighted-average lead concentration (ppm Pb) in

sediments deposited above the 1980 volcanic-ash layer. (A value of -999 indicates no

data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 0.16

 Range_Domain_Maximum: 2.58

 Attribute_Units_of_Measure: ratio

 Attribute:

 Attribute_Label: JBA_PB

 Attribute_Definition: JBA LEAD - Concentration of lead (ppm Pb) in the sample 

interval immediately below the base of the 1980 volcanic-ash layer. (A value of -999

indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 66

 Range_Domain_Maximum: 9810

 Attribute_Units_of_Measure: ppm (parts per million)

 Attribute:

 Attribute_Label: BA1_PB

 Attribute_Definition: BA1 LEAD - Concentration of lead (ppm Pb) in sediments 

of the BA1 stratigraphic interval (defined above). (A value of -999 indicates no 

data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: 1500

 Range_Domain_Maximum: 6735

 Attribute_Units_of_Measure: ppm (parts per million)

 Attribute:

 Attribute_Label: PBAA_BA1

 Attribute_Definition: Ratio of lead concentration in sediments above the 1980 

Mt. St. Helens ash intervals to the concentration of lead in sediments below the 

1980 Mt. St. Helens ash interval. (A value of -999 indicates no data.)

 Attribute_Domain_Values:

 Range_Domain:

 Range_Domain_Minimum: .33

 Range_Domain_Maximum: 1.52

 Attribute_Units_of_Measure: ratio

 Overview_Description:

 Entity_and_Attribute_Overview: This metadata describes one geospatial dataset 

CDA_SR_PB shapefile (an ESRI-format file). The shapefile consists of five individual

files: CDA_SR_PB.SHP, CDA_SR_PB.SHX, CDA_SR_PB.DBF, CDA_SR_PB.SBN, CDA_SR_PB.SBX 

Page 13
cda_sr_pb-of_meta.txt

that together provide spatial data. An ArcView (ver. 3.2) legend, CDA_SR_PB.SHX, was

created (and included) to symbolize the post-1980 sedimentation (measured in 

cm/decade). A "-999" in any of the shapefile attributes denotes "no useable data".

Distribution_Information:

 Distributor:

 Contact_Information:

 Contact_Organization_Primary:

 Contact_Organization: U.S. Geological Survey

 Contact_Electronic_Mail_Address: http://pubs.usgs.gov/of/2004-1211

 Contact_Instructions: This report is only available in an electronic format at

the following: URL= http://geopubs.usgs.gov/of/04-1211

 Resource_Description: Downloadable Data

 Distribution_Liability: The U.S. Geological Survey (USGS) provides this data "as 

is". The USGS makes no guarantee or warranty concerning the accuracy of information 

contained in the geographic data. The USGS further makes no warranties, either 

expressed or implied as to any other matter whatsoever, including, without 

limitation, the condition of the product, or its fitness for any particular purpose.

The burden for determining fitness for use lies entirely with the user. Although 

this data has been processed successfully on computers at the USGS, no warranty, 

expressed or implied, is made by the USGS regarding the use of this data on any 

other system, nor does the fact of distribution constitute or imply any such 

warranty. In no event shall the USGS have any liability whatsoever for payment of 

any consequential, incidental, indirect, special, or tort damages of any kind, 

including, but not limited to, any loss of profits arising out of use of or reliance

on the geographic data or arising out of the delivery, installation, operation, or 

support by the USGS.

 Standard_Order_Process:

 Digital_Form:

 Digital_Transfer_Information:

 Format_Name: ARCE

 Format_Version_Number: 9.0

 Transfer_Size: 0.004

 Fees: none

 Ordering_Instructions: This report is available only in electronic format either

for purchase on CD-ROM from USGS Information Services OR at no cost from URL = 

http://pubs.usgs.gov/of/04-1211.

 Custom_Order_Process: none

 Technical_Prerequisites: ESRI ArcGIS (Workstation ArcInfo, ArcMap, or ArcView) 

software.

Metadata_Reference_Information:

 Metadata_Date: 2005 Feb 18

 Metadata_Contact:

 Contact_Information:

 Contact_Organization_Primary:

 Contact_Organization: Information Systems Support, Inc. (under contract to 

the U.S. Geological Survey)

 Contact_Person: John C. Wallis , Helen Z. Kayser

 Contact_Position: GIS Specialists

 Contact_Address:

 Address_Type: mailing and physical address

 Address: 904 W. Riverside Avenue, Rm. 202

 City: Spokane

 State_or_Province: Washington

 Postal_Code: 99201

 Country: USA

 Contact_Voice_Telephone: 1-509-368-3108, 1-509-368-3162

 Contact_Facsimile_Telephone: 1-509-368-3199

 Contact_Electronic_Mail_Address: jwallis@usgs.gov, hkayser@usgs.gov

 Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata

 Metadata_Standard_Version: FGDC-STD-001-1998

 Metadata_Time_Convention: local time

 Metadata_Access_Constraints: none

 Metadata_Use_Constraints: none

Page 14
cda_sr_pb-of_meta.txt

 Metadata_Extensions:

 Online_Linkage: http://www.esri.com/metadata/esriprof80.html

 Profile_Name: ESRI Metadata Profile

Page 15

Osburn

 Fault

 Gem

 Stocks

Coeur d'Alene

Smelterville Kellogg

Rose Cataldo

 Bunker Hill

Superfund Site

Wallace

Osburn

Coeur d'Alene Mining District 

Mullan

7o

30'

Coeur 

d'Alene 

Lake

North Fork 

Harrison

 St. Joe

 River

Burke

Coeur d'Alene

 River

SouthFork

Kingston

Spokane River

0

10

20

River miles below Mullan

60

50

40

30

40

Elizabeth

 Park

o

st Falls

Dam

Wolf Lodge Bay

East Pt.

Gasser Pt.

Fuller's Bay

Conkling Pt.

Pinehurst

Pine Cr.

gure 2. Index and location maps, showing selected features of the Coeur d'Alene (CdA) mining district, the Bunker Hill Superfund Site,

the South and North Forks, the CdA River and its lateral lakes, the lower St. Joe River, CdA Lake, and the upper Spokane River.

*

*

* * *

*

* *

*

*

*

*

*

Enaville

*

10 Km

N 10 Mi

OR

MT

ID WY

AREA

 OF

 MAP

WA

116

Ninemile Cr.

Canyon Cr.

City or town site *

Prichard Cr.

Murray *

lower

middle

Lake

upper

Rathdrum Prairie
47 35' o

47 32' 30" o

Bull

Run

Cr.

(Upper Perennial Subsystem)

2200

>2200

2200

>2200

R1

R2

R0

Rose Lake

Rose 

Lake

Porter 

Slough

 Orling

Slough

Canyon

 Marsh

Dudley

Dudley 

 Meadow

dt Frutchey's

Meadow

Mission

Slough

Cataldo

Slough

Cataldo Lead 

 Flats Kingston

Enaville

Upper Part, Coeur d'Alene River valley

*

*

*

ct

*

Cataldo

Terraces

#

Fourth

of July

Cr.

N

o

rth

Fork

South Fork

CdA River

French

Cr.

2200

2200

>2200

>2200

Figure 3. Location map of the Upper CdA River valley, showing the river and the 2,200 ft elevation contour along the hillsides 

 that bound the floodplain. Also shown are locations and names of features described in the text: = town, # = sawmill site

 (abandoned), cl = Cataldo Landing (x), ct = Cataldo drill transect, dt = Dudley drill transect, mb = McPhee Bridge, 

 eb = Enaville Bridge, erb = Enaville railroad bridge, crb = Cataldo railrooad bridge, chb = Cataldo state highway bridge,

 cib = Cataldo interstate highway I-90 bridge; R2, R1, R0 = River reaches.

* 

116 25' 116 20' 116 15' o o o

 Kingston segment

 (upper a) (upper b) Dudley segment

 (upper c)

0

0 1 2 3

Km

1 2

Mi

Scale

x

cl

Skeel G. .

mb

eb

erb

chb

cib

crb

#

Cataldo segment

 Latour

 Terraces

Whiteman's

Slough

Cataldo

*

Mission Mission 

Terraces

Latour

Cr.

Cataldo 

Flats

Braided, gravel-bottomed channel

Meandering, sand-bottomed channel

Bull Run

Lake

*

(Lower Perennial Subsystem)

>2200

>2200

2200

2200

R0
o

o

116 35

 Killarney 

 Lake

Blessing

Slough 

Moffit

Slough

 Meadow

Sawmill

Blackrock Slough

west

east

 Bull Run

Lake

Medimont

Evans Cr.

>2200

Blackrock Cr.

2200

2200

Bull Run Cr.

Clark Cr.

Robinson Cr.

central

north

 47 32' 30"

47 30'

Schlepp's 

Med. Marsh

Meadows

>2200

>2200

2200

2200

>2200

>2200

2200

>2200

>2200

>2200

>2200

2200

2200

>2200

R5

R4

R4

R3

R3 R2

Lane Marsh

north

south

Lane

Gleason's

Meadow

Rose Lake

Rose

 Lake

 valley

 Rose 

Lake

Porter 

Slough

Canyon

 Marsh

 Dudley 

Meadow

Middle Part, Coeur d'Alene River valley

*

kt

#

2200

Swa

n

Cr.

Willow Cr.

 mt

Rose Lake

Fortier Cr

 Location map of the Middle CdA River valley, showing

 	 the river and the 2,200 ft elevation contour along the hillsides, 

	 	 which bound the floodplain. Also shown are locations and names

	 	 of lateral lakes, marshes, sloughs, meadows, tributary creeks, and 

	 	 other features described in the text: = town, # = sawmill site 

 	 (abandoned), kt = Killarney drill transect, mt = Moffit drill transect,

	 	 rlb = Rose Lake Bridge, h3b = Highway 3 Bridge;

	 	 R2, R3, R4 = River reaches. 

 	

*

Figure 4. 

Cr.

#

116 30

0

0 1 2 3

Km

1 2

Mi

Scale

 rlb

h3b

Killarney Cr

 Medicine 

Cave Lake Lake

*

*

Strobl Marsh

Hidden

 Marsh

Ca mpbell Marsh

*

Dudley

Rose Lake seg.

 (middle a)

 Lane segment

 (middle b)

 Killarney segment

 (middle c)

(Lower Perennial Subsystem)

>2200
Thompson Marsh

Cave Lake

Harrison

Anderson Lake

Thompson 

 Lake

Blue Lake

Black Lake

Swan Lake

Harrison

 Slough

Springston

Meadow

Bare Marsh

Blue Marsh

Swan 

Marsh

Blessing

Slough 

Medimont

Lower Part, Coeur d'Alene River valley

*

ht

st

*

#

2200

Thompson

Cr.

Blu e Lk. Cr.

Bell Canyon

Lamb Cr.

Black Cr.

Figure 5. Location map of the Lower CdA River valley, showing the river and

 the 2,200 ft elevation contour along the hillsides, which bound the floodplain.

 Also shown are locations of lakes, marshes, sloughs, meadows, tributary creeks,

 and other features described in the text: = town, # = sawmill site (abandoned), 

 st = Swan drill transect, ht = Harrison drill transect, sb = Springston bridge,

 hb = Harrison bridge, h96 = Highway 96 embankment; R4, R5, R6 = River reaches.

* 

116 45' o 116 40' o

47 30' o

o 47 25'

 Pring Meadow

west

 ( Harrison Arm ) h96

Pring Meadow

east

Coeur d'Alene Lake

(St. Joe Arm)

Harrison segment

2200

Delta

front

(lower c)

Medicine

Mtn. Cave

Marsh

Harrison

Marsh

2200

>2200

>2200 >2200

>2200

2200

R5

R6

R5

R4

R6

0

0 1 2 3

Km

1 2

Mi

Scale

Medimont segment

(lower a)

sb

hb

Blue Lake segment

(lower b)

(Lower Perennial Subsystem)


	




  





 

Distributwith leve

Point bar depositof storedPb-richsediments

Figure 6. Schematic block diagram, showing features typical of the meandering, sand-bottomed  floodplain, between Cataldo Landing and Harrison (modified from Reineck and Singh and Leopold, 1997). SWL indicates summer water lever, and WWL indicates winter w represent flow paths. Dark grays on steep faces indicate the section of Pb-rich sedime

 indicates highest-Pb sediments, deposited during jig-tailings disposal.



Natural 

Levee

 Secondary circulation



 ! "# !$ 
#

SWL Pb-rich jig-interval seds, and f

	% #


#!"& '" #&

!	 (

!	 )

Bank-wedge deposit of Pb-rich sediments,

Pre-mining s

 *! +",

$ 
!

Pre-mining levee 

 Bank-wedge (eroded)

!	 - *-./0,

Channel-deep (thalweg)

River channel

pre-mining bottom active sed

stored sed

Pre-miningpoint bar deposits

Pre-mining sediments

Bedrock

Meander scr(pre-mining p

WWL

Levee sand 
!


!1 	#


"#

"#


%1

Litt
Figure 7a. Graphs showing annual production of ore, Pb and Zn, and major related events. Data are from Ransome

 and Calkins (1908), Fryklund (1964), Mitchell and Bennett (1983), U.S. Bureau of Mines Yearbooks (1980-1990).

ANNUAL PRODUCTION, CDA MINING DISTRICT, 1886 TO 1990

0

1

2

3

1885 1905 1925 1945 1965 1985

YEAR

ORE (MEGA TONNES)

0

0.05

0.1

0.15

0.2

METALS (MEGA TONNES)

Ore

Pb

Zn

Jig interval

Flotation interval

Post-tailings-release time

Post-1980

baseline

time

Tailings 

lawsuit

Jig-flotation transition

1903

~1912

~1929

~1920

1968 1980

WW I WW II

Bunker converts

to flotation

~1937

Depression

Post-war

boom

Cold-war

 era

Worldtrade

era

Ag production > 340 t/y
Figure 7b. Time line showing important events in the history of tailings management in the context

 of annual production (SF = Smelterville Flats, O = Osburn Flats, CC = Canyon Creek). 

ANNUAL PRODUCTION, CDA MINING DISTRICT, 1886 TO 1990

0

1

2

3

1885 1905 1925 1945 1965 1985

YEAR

ORE (MEGA TONNES)

0

0.05

0.1

0.15

0.2

METALS (MEGA TONNES)

Pb Ore

Zn

Jig interval

Flotation interval

Post-tailings-release time

Post-1980

baseline

time

Tailings 

lawsuit 

of 1903

Jig-flotation transition

1968 1980

1893-'94 

floods

SF, O, CC

tailings dams

built 1901-07

O, CC tailings dams

destroyed by

floods of 1917

SF tailings dam

 destroyed by

 major flood

 of 1933

Dredge at Cataldo Flats (1932-67)

Bunker converts

 to flotation

 ~1937

Major flood

of 1974

Sand fraction of tailings used for backfill

Bunker Tailings Impoundment (1928-81) 

Tailings

reprocessing
10

0

20

40

0

20

40

60

80

0

20

40

60

80

100

120

140

0

6000

12,00018,000

24,000

30,000

ppm Pb

cm

cm

1,0005,000

ppm Pb

0

5,000

10,000

15,000

20,000

25,000

ppm Pb

0 3,000 6,000

ppm Pb 0 3,000 6,000

cm

BG -- peat

1980 volcanic ash

Bull Run Lake 

Rose Lake

50

cm

ppm Pb

Figure 8. Lead-concentration profiles for stratigraphic sections of Pb-rich

sediments of the Coeur d'Alene River and its floodplain. River-channel, 

riverbank, and marsh profiles are from data of Box and others (2001). 

Bull Run and Rose Lake profiles are from data of Rabbi (1994). Porters

Lake profile is from Sprenke and others (2000). Intervals (AA, BA1, BA2F

BA2J, and BG) are defined in text and table 1. Profile scales are different. 

 

 olive gray colored

 medium sand,

 with darker,

 finer-grained

 interbeds

 

 light olive colored 

 medium sand, 

 poorly stratified

 (active bed sediment)

(600 m from river) 

(300 m from river)

(1700 m from river)

(Down hole contamination is probable

 in this drill hole. Pre-mining-era sediment

 contains 25 ppm Pb in a nearby drill hole

 with no overlying metal-enriched

 sediments.) 

 fine red-brown sand,

 silty interbeds 

 (orange-brown) 

black mud

silty mud and duff

BA2F

BA2J

pm

dark gray silty mud

0

25

50

500010,000

ppm Pb

cm

Porters Lake

(680 m from river)

~1903

~1918

~1968

BA2J

BA2F

jig-tailings-release

flotationtailingsrelease

posttailingsrelease

very fine sand

sandy silt

BG: gray silty mud with sand interbeds

BA2J

jig-tailings release

AA

BA2F BA1

flotationtailings release

BA2J jig-tailings release

(no 1980 ash layer)

detrital galena

and sphalerite

Zn/Pb >=1

 Pb, Zn ions adsorbed

 on Mn and Fe oxides

 Zn/Pb <=1

 (Zn leached)

Pb, Zn in biogenic 

 sulfidic phases 
Figure 9. Cumulative frequency diagram showing baseline sediment-deposition rates (sdrAA) 

for sediments deposited on the floodplain from 1980 to about 1993.

CUMULATIVE FREQUENCY OF BASELINE SEDIMENT-DEPOSITION RATES (1980 ~1993)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5 10 15 20 25 30

BASELINE SEDIMENT-DEPOSITION RATE (CM/10Y)

PROPORTION OF SITES

Floodplain total n = 125

Riverbank n = 47

Upland n = 49

Palustrine n = 18

Littoral n = 7

Limnetic n = 4
Figure 10. Scatter diagram showing baseline sediment-deposition rates (sdrAA) versus 

distance (m) from the CdA River. Sample sites are classified by depositional setting.

BASELINE SEDIMENT-DEPOSITION RATES VERSUS DISTANCE FROM THE RIVER

0

5

10

15

20

25

30

0 500 1000 1500 2000 2500

DISTANCE FROM THE CDA RIVER (M)

BASELINE SEDIMENT-DEPOSITION RATE (CM/10Y)

Floodplain total n = 125

Riverbank n = 47

Upland n = 49 

Palustrine n = 18 

Littoral n = 7

Limnetic n = 4
Figure 11. Frequency diagram of baseline sediment-deposition rates (sdrAA).

BASELINE SEDIMENT-DEPOSITION RATES (1980 ~1993)

05

101520253035404550

0.0-2.0 2.1-4.0 4.1-6.0 6.1-8.0 8.1-

10.0

10.1-

12.0

12.1-

14.0

14.1-

16.0

16.1-

18.0

18.1-

20.0

20.1-

22.0

22.1-

24.0

24.1-

26.0

26.1-

28.0

28.1-

30.0

BASELINE SEDIMENT-DEPOSITION RATE (CM/10Y)

SITE COUNT (BY DEPOSITIONAL SETTING) Floodplain total n = 125 Riverbank n = 47 Upland n = 49 Palustrine n = 18 Littoral n = 7 Limnetic n = 4
Figure 12. Frequency diagram of natural logs of baseline sediment-deposition rates (ln sdrAA).

LN OF BASELINE SEDIMENT-DEPOSITION RATES (1980 ~1993)

0

5

10

15

20

25

30

35

40

-1.0 to -

0.6

-0.6 to -

0.2

-0.2 to

+0.2

0.2 to 0.6 0.6 to 1.0 1.0 to 1.4 1.4 to 1.8 1.8 to 2.2 2.2 to 2.6 2.6 to 3.0 3.0 to 3.4

NATURAL LOG OF BASELINE SEDIMENT-DEPOSITION RATE (LN CM/10Y)

SITE COUNT (BY DEPOSITIONAL SETTING)

Floodplain total n = 122

Riverbank n = 47

Upland n = 47

Palustrine n = 17

Littoral n = 7

Limnetic n = 4
Figure 13. Cumulative frequency distribution of baseline lead concentrations (PbAA) 

in floodplain sediments of the AA (after-ash) time-stratigraphic interval (1980 ~1993).

CUMULATIVE FREQUENCY OF LEAD CONCENTRATIONS

IN SEDIMENTS OF THE BASELINE INTERVAL (1980 ~1993)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1000 2000 3000 4000 5000 6000 7000 8000

BASELINE LEAD CONCENTRATION (PPM PB)

PROPORTION OF SITES

Floodplain total n = 90

Riverbank n = 20

Upland n = 44

Palustrine n = 16

Littoral n = 7

Limnetic n = 3
Figure 14. Scatter diagram showing lead concentrations (ppm Pb) in floodplain sediments of the 

baseline (AA) time-stratigraphic interval (1980 ~1993) versus distance from the CdA River.

LEAD IN BASELINE (AA) SEDIMENTS VERSUS DISTANCE FROM THE RIVER

0

1000

2000

3000

4000

5000

6000

7000

8000

0 500 1000 1500 2000 2500

DISTANCE FROM CDA RIVER (M)

BASELINE LEAD (PPM PB)

Floodplain total n = 90

Riverbank n = 20

Upland n = 44 

Palustrine n = 16

Littoral n = 7

Limnetic n = 3
Figure 15. Frequency diagram of baseline lead concentrations (PbAA) in lead-rich 

floodplain sediments of the AA time-stratigraphic interval (1980 ~1993). 

BASELINE LEAD CONCENTRATIONS IN SEDIMENTS OF THE AA INTERVAL (1980 ~1993)

0

5

10

15

20

25

1001-2000 2001-3000 3001-4000 4001-5000 5001-6000 6001-7000 7001-8000 8001-9000

BASELINE LEAD CONCENTRATION (PPM PB)

SITE COUNT

Floodplain total n = 77

Riverbank n = 20

Upland n = 40

Palustrine n = 9

Littoral n = 5

Limnetic n = 3
Figure 16. Frequency diagram of natural logs of baseline lead concentrations (PbAA) 

in Pb-rich floodplain sediments of the AA time-stratigraphic interval (1980 ~1993).

NATURAL LOG OF BASELINE LEAD IN SEDIMENTS OF THE AA INTERVAL (1980 ~1993)

0

2

4

6

8

10

12

14

16

18

6.60-6.75 6.76-7.00 7.01-7.25 7.26-7.50 7.51-7.75 7.76-8.00 8.01-8.25 8.26-8.50 8.51-8.75 8.76-9.00 9.01-9.14

NATURAL LOG OF BASELINE LEAD CONCENTRATION (LN PPM PB)

SITE COUNT BY DEPOSITIONAL SETTING

Floodplain total n = 80

Riverbank n = 20

Upland = 43

Palustrine n = 9

Littoral n = 5

Limnetic n = 3
0

5

10

15

20

25

30

35

40

SEDIMENT-DEPOSITION RATE (CM/10Y)

sdrBA (~1903 - 1980) sdrAA (1980 ~1993)

Figure 17. Box-and-whisker plots, comparing sediment-deposition rates

for sediments of the historic (BA) and baseline (AA) time-stratigraphic 

intervals.

90th percentile

75th

50th

25th

10th

4.7

3.6

n = 46 n = 46
Figure 18. Scatter diagram showing rates of deposition of lead-rich sediments for paired baseline (AA) 

and historic (BA) time-stratigraphic intervals, as a function of distance from the CdA River.

BASELINE AND HISTORIC SEDIMENT-DEPOSITION-RATES 

VERSUS DISTANCE FROM THE RIVER

0

5

10

15

20

25

30

35

40

0 500 1000 1500 2000 2500

DISTANCE FROM CDA RIVER (M)

SEDIMENT-DEPOSITION RATE (CM/10Y)

sdrAA riverbank n = 22

sdrAA upland n = 14

sdrAA palustrine n = 7

sdrAA limnetic n = 3

sdrAA floodplain total = 46 

sdrBA riverbank n = 22

sdrBA upland n = 14

sdrBA palustrine n = 7

sdrBA limnetic n = 3

sdrBA floodplain total n = 46 
Figure 19. Cumulative frequency distribution of thickness-weighted average lead concentration 

in floodplain sediments of the historic (BA) time-stratigraphic interval (~1903 - 1980). 

CUMULATIVE FREQUENCY OF LEAD CONCENTRATIONS 

IN SEDIMENTS OF THE HISTORIC (BA) INTERVAL (~1903-1980)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000

HISTORIC LEAD CONCENTRATION (PPM PB)

PROPORTION OF SITES

Floodplain total n = 28

Riverbank n = 7

Upland n = 13

Palustrine n = 4

Littoral n = 1 

Limnetic n = 3 
Figure 20. Scatter diagram showing thickness-weighted average lead concentration ( ppm Pb)

 in sediments of the historic (BA) interval (~1903-1980) versus distance from the CdA River.

LEAD IN HISTORIC (BA) SEDIMENTS VERSUS DISTANCE FROM THE RIVER

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

0 500 1000 1500 2000 2500

DISTANCE FROM CDA RIVER (M)

HISTORIC LEAD (PPM PB)

Floodplain total n = 28

Riverbank n = 7

Upland n = 13

Palustrine n = 4

Littoral n = 1

Limnetic n = 3
Figure 21. Box-and-whisker plots, comparing interval-weighted average

 lead (ppm Pb) in sediments of the historic (BA) and baseline (AA)

 time-stratigraphic intervals.

n = 28 n = 28

90th percentile

75th

50th

25th

10th

5400

3100

0

2000

4000

6000

8000

10000

12000

14000

16000

INTERVAL-WTD AVERAGE LEAD (PPM PB)

PbBA (~1903 - 1980) PbAA (1980 ~1993)

5400

3100
Figure 22. Summary plot showing sediment-deposition-rate statistics for sediments of BG (background),

EME (early metals-enrichment), BA2 (tailings-release), BA1 (early post-tailings), and AA (baseline) intervals. 

SEDIMENT-DEPOSITION RATES BY TIME INTERVAL

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

YEAR

SEDIMENT-DEPOSITION RATE(CM/10Y)

AA maximum

AA mean + stdev

AA mean

sdrAA geo mean

sdrAA median

sdrAA area wtd av, ds meds

sdrAA mode

sdrAA mean - stdev

sdrAA minimum

sdrBA1 maximum

sdrBA1 median (sdrAA + 10%)

sdrBA1 minimum

BA2 maximum

BA2 mean + stdev

BA2 mean

BA2 geo mean

BA2 median

BA2 area wtd av of medians

BA2 mode

BA2 mean - stdev

BA2 minimum

BG maximum

BG median

1903

Tailings

lawsuit

1886

Mining

onset

1893-94

Major

floods

1980

ash

BG BA2 BA1 AA

1933

Major

flood

1932-1967 Dredging

(See table 11 for AA and BA rates. BA1 is assumed = AA + 10%. BA2 is calculated from BA and BA1.) 

1974

Major

flood

1996

Major 

flood

EME

 ~1968

 Last tailings

 to streams

~1950 - 2003 Tailing-sand to backfill

 ~1993

sampling
0

2000

4000

6000

8000

10000

12000

14000

16000

INTERVAL-WTD AVERAGE LEAD (PPM PB)

PbBA1 (1968 - 1980) PbAA (1980 ~1993)

Figure 23. Box-and-whisker plots, comparing interval-weighted average lead 

(ppm Pb) in sediments of the early post-tailings-release (BA1) and baseline (AA) 

time-stratigraphic intervals.

n = 13 n = 13

90th percentile

75th

50th

25th

10th

4000

3300
Figure 24. Summary plot of lead-concentration statistics (in ppm) for sediments of BG (background), EME (early metals-enrichment), 

BA2J (jig), BA2 (tailings-release), BA1 (early post-tailings), and AA (baseline) intervals.

LEAD IN FLOODPLAIN SEDIMENTS BY TIME INTERVAL

0

2000

4000

6000

8000

10000

12000

14000

16000

1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

YEAR

LEAD (PPM PB)

AA maximum

AA mean + stdev

AA mean

AA geo mean

AA median

AA area wtd av of medians

AA mean - stdev

AA minimum

BA1 maximum

BA1 mean + stdev

BA1 mean

BA1 geo mean

BA1 median

BA1 area wtd av of medians

BA1 mean - stdev

BA1 minimum

BA2 maximum

BA2 mean + stdev

BA2 mean

BA2 geo mean

BA2 median

BA2 area wtd av of medians

BA2 mean - stdev

BA2 minimum

BG maximum

BG mean + stdev

BG mean

BG median

BG mode

BG mean - stdev

BG minimum

BG BA2J BA2 BA1 AA

1886

Mining

onset

1893-94

Major

floods

1903

Tailings

lawsuit

1932-1967 Dredging

1933 

Major 

flood

~ 1950 - 2003 Tailings-sand to backfill

1974

Major

flood

1996

Major

flood

[See table 15 for PbAA and PbBA1. PbBA2 is calculated from PbBA (table 15) and PbBA1.] 

EME

 

 ~1968

Last tailings

 to streams

 up to

 37,000

ppm Pb

1980

 ash

 ~1993

sampling
Table 1. Stratigraphic Section of Lead-Rich Sediments from the toe of the Coeur d'Alene River delta in Coeur d'Alene Lake 

(data from Horowitz and others, 1995, core sample H123)*

Sediments

Depth 

(cm)

Lead 

concentrations, 

from base to top 

of interval 

(approx. ppm Pb)

Years 

(beginning to end 

of time span)

Thickness 

(depth 

span)

Time span 

Sedimentdeposition 

rate 

(sdr)

 Timeaveraged 

interval 

(sdr) 

 Timestrat 

interval 

(wtd av) 

top of core (cm) (y) (cm/10y)

Volcanic ash 20-21.5 1300 1980 1

21.5-40 5900 

2700 ~1968 - 1980 18.5 10 18.5

40-46

1964

~1954

75-80

90-95 6500 5 4 12.5

95-100 16,000 5 5 10.0

100-105 27,500 5 5 10.0

105-110 8,000 5 5 10.0

~900 ~1903 to 1990 110 85

~100 ~1895 - 1903 9 ~10 ~11

199-126 ~12 to ~100 before ~1895 7 ~70 ~1

~1825 to 1990 126 ~165 ~8

EME 

~500 ppm Pb

12.9 PBR ~7100 ppm

BA2 

~8000 

ppm 

BA2J 

17,000 

ppm 

BA2F 

~4900 

ppm

BA2 

(tailings 

release) 

11 

10 18

Time marker, time interval, 

or time-span of tailings 

production and 

management

Layered sediments 1980 - 1990 20.5

sample-collection date

0-20.5 Pre-remedial baseline 

interval (AA)

6000 

4600

(WWII production peak)

14

~1940 - 1945 5 5 10.0

14.3

15 9 16.7

Flotation-tailings (BA2F) 

(river dredging after 1932)

Jig-flotation transition 

(WWI production peak)

Layered 

sediments: 

thin tan to brown 

layers with thinner, 

darker brown to 

black interlayers

60-75

46-60

80-90

8200 

8500

Flotation-tailings

137Cs onset

Flotation-tailings-release 

sub-subinterval (BA2F)

5.6

10 20.5

20

b. median of background concentrations in CdA Lake-bottom sediments below the section of Pb-enriched sediments

BA 

~ 7500 

ppm

Mt. St. Helens ash Ash ~1300 ppm Pb

BA 

(below 

or before 

ash) 

12 

*Time-stratigraphic intervals interpreted from stratigraphic, Cs isotopic, and Pb-concentration data from core 123 of Horowitz and others (1995)

a. by analogy with the pre-mining-era sedimentation rate in Killarney Lake, as estimated by Sprenke and others (2000) 

Early post-tailings-release 

subinterval (BA1) 

(also post-river dredging)

BG (background) 

~1 a

4000

BG 

(33 ppm Pb) Background section (BG) b

Non-layered 

sediments

Early metal-enrichment 

interval (EME)

110-119

Top to bottom of core

Pb-rich section (PBR)

EME (early metal-enrichment) 

~11 

BA1 

~4300 ppm 

Time-strat 

sub-interval 

(wtd av)

(cm/10y)

Time-averaged 

sub-interval 

(sdr)

(approx. ppm Pb)

BA1 

(early post-tailings) 

19 

AA 

~ 5300 ppm Pb 

Ash 

AA 

(above or after ash) 

21 

Bottom of core

2700 

4000

6200 

6500

BA2J 

(jig) 

10

BA2F 

(flotation) 

11 

1903 + 8y 

to 1918 + 5

1918 + 6 

to ~1940

Jig-tailings-release 

(BA2J) sub-subinterval

137Cs peak

Flotation-tailings (BA2F)
Table 2. Sediment-Deposition Rates and Lead Concentrations, Coeur d'Alene Lake-Bottom Sediments,

 below and above the 1980 Volcanic-Ash Layer (after Horowitz and others, 1993, 1995*)

sdrBA 

(Before 

Ash)

1980 

volcanic 

ash layer

sdrAA 

(After 

Ash) 

cm/10y cm/y cm/10y

Delta Toe 123 NW 1.5 11.5 1.0 20.5 1.90 123 6000

8 SE 3.5 1.8 0.2 9.6 5.33 LC10264 1460

6 NW 4.9 nd 1.5 5.0 nd LC10247 3200

mean 6.7 0.9 11.7 3550

mean aa /mean ba 1.86

Lake Bays

Windy 9 NW 11.9 3.3 0.2 3.5 1.06 LC10229 880

Wolf Lodge 10 NNE 40.6 2.3 0.2 2.3 1.00 LC10160 540

mean 2.8 0.2 2.9 710

mean aa /mean ba 1.04

Lake Axis 93 NNW 11.9 3.2 0.3 0.5 0.16 LC10211 2150

71 N 19.4 2.6 0.2 0.5 0.19 LC10196 2020

47 N 26.1 2.7 0.1 0.3 0.11 LC10171 6830

mean 2.8 0.2 0.4 3670

mean aa /mean ba 0.14

sample ppm Pb

CdA Lake 

depositional 

environment

Kilometers 

from 

mouth of 

CdA River

Sediment-deposition rates

Time intervals

Sediment-deposition rates

*based on data from Horowitz and others (1993) in USEPA (2001), and Horowitz and others (1995)

~1903 

to 1980

May-Oct 

1980

1980 

to 1990

 Sedimentdeposition-rate 

(sdr) ratio

Gravity 

core-hole 

number

Direction 

from river 

mouth

Lead concentration 

in lake-bottom 

surface sample 

nearest core site

sdrAA / sdrBA
Table 3. Baseline Sediment-Deposition Rates (sdrAA) for Floodplain Sediments

 of Time-Stratigraphic Interval AA (1980 ~1993)

Riverbank Upland Palustrine

littoral limnetic

(lt) (lm)

sites:ash-layer (a), freeze-box (f) n 26 a 22 a 7 a 0 0

min sdrAA to max sdrAA cm/10y 1 to 29 0 to 12 0.1 to 8 no data no data

arithmetic mean + stdev of sdrAA cm/10y 8.1 + 6.2 3.0 + 2.3 3.3 + 2.0

coefficient of variation (CV) 0.76 0.77 0.61

geometric mean of sdrAA cm/10y 6.0 2.8 2.8

median of sdrAA cm/10y 6.5 3.0 2.0

sites:ash-layer (a), freeze-box (f) n 9 a 21 a 8 a 3 a 3 f

min sdrAA to max sdrAA cm/10y 2 to 11 1 to 21 0 to 4 0.5 to 3 3.6 to 4.5

arithmetic mean + stdev of sdrAA cm/10y 5.3 + 3.0 4.8 + 5.1 2.1 + 1.4 1.5 + 1.3 4.4 + 0.5

coefficient of variation (CV) 0.57 1.06 0.67 0.87 0.12

geometric mean of sdrAA cm/10y 4.2 3.2 2.1 1.2 4.1

median of sdrAA cm/10y 5.0 2.0 2.0 1.2 4.3

sites:ash-layer (a), freeze-box (f) n 12 a 6 a 3 a 4 a 1 f

min sdrAA to max sdrAA cm/10y 1 to 12 1 to 4 1 to 3 1 to 4 2.7

arithmetic mean + stdev of sdrAA cm/10y 5.5 + 4.0 2.8 + 1.0 1.8 + 1.1 3.0 + 1.3 2.7

coefficient of variation (CV) 0.73 0.36 0.61 0.43 0.00

geometric mean of sdrAA cm/10y 4.3 2.7 1.7 2.7 2.7

median of sdrAA cm/10y 5.0 2.5 1.5 3.4 2.7

sites:ash-layer (a), freeze-box (f) n 47 a 49 a 18 a 7 a 4 f 125

min sdrAA to max sdrAA cm/10y 1 to 29 0 to 21 0 to 8 0.5 to 4 2.7 to 4.5 0 to 29

mode of sdrAA 1.9 3.9 1.0 1.2 3.9

arithmetic mean + stdev of drAA cm/10y 6.9 + 5.3 3.7 + 3.8 2.5 + 1.7 2.4 + 1.4 3.8 + 0.8 4.7 + 4.3

coefficient of variation (CV) 0.77 1.03 0.68 0.58 0.21 0.91

peakedness 5.00 8.42 4.19 -1.88 -0.61 7.44

peakedness (ln of data) -0.55 -0.89 -0.31 -0.12 0.29 -0.29

skewness 1.75 2.71 1.59 -0.19 -0.89 2.33

skewness (ln of data) -0.32 -0.90 -0.20 -0.98 -1.12 0.26

geometric mean of sdrAA cm/10y 5.1 3.0 2.2 1.9 3.7 3.5

median of sdrAA cm/10y 6.4 2.8 2.2 2.9 4.0 3.1

fp area of Pb-rich sedimentsa

km2

2.2 14.0 19.6 8.3 9.6 53.7

(nlm ds km2) / (nlm fp fldpln km2) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(anlm ds / anlm fp)(med sdrAA) 0.26 + 0.73 + 0.79 + 0.44 +0.72 = 2.94

area-wtd average of medians cm/10y 2.9

df

37

83

83

34

10

9

62

22

23

28

14

19

sdrAA (u) > sdrAA(p) 0.07

0.05

85% (probably different)

sdrAA(u) < sdrAA(lm) 0.95 5% (practically not different)

0.08

0.10

Entire 

floodplain 

(fp)

93% (probably different)

sdrAA(p) > sdrAA(lt) 0.90 10% (probably not different)

sdrAA(u,fpu) < sdrAA(u,fpm)

sdrAA(rb) > sdrAA(p)

sdrAA(u) > sdrAA(lt)

sdrAA(u,fpm) > sdrAA(u,fpl)

sdrAA(lt) < sdrAA(lm)

0.001

sdrAA(p) < sdrAA(lm)

0.06

sdrAA(rb) > sdrAA(lm)

relative difference in means

sdrAA(rb) > sdrAA(lt)

sdrAA(rb) > sdrAA(u)

Entire main 

stem, CdA 

River 

probability of difference in populationsb

Area-wtd 

average of 

med sed 

rates

(u) (p)

Floodplain 

Segment

Summary statistics, 

baseline sediment-deposition rates 

(sdrAA), floodplain sediments, 

AA time-stratigraphic interval, 

(deposited after the 1980 volcanic ash) 

Units

(rb)

P(T>=t) two-tail

Sedimentary environment (se) 

Levee (lv)

Lacustrine

Flood basin (fb)

Depositional setting (ds)

100% (significantly different)

0.15

92% (probably different)

90% (probably different)

99.9% (significantly different)

99.9% (significantly different)

99.9% (significantly different)

94% (probably different)

95% (significantly different)

b. Probability that these two compared data sets represent populations that are statistically different.

Upper main 

stem, CdA 

River 

floodplain 

(fpu)

Middle 

main stem, 

CdA River 

floodplain 

(fpm) 

Lower main 

stem, CdA 

River 

floodplain 

(fpl)

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

0.00002

0.001

0.001
Table 4. Baseline Lead Concentrations (PbAA) in Lead-Rich Floodplain Sediments of Time-Stratigraphic Interval AA (1980 ~1993)

Riverbank Upland Palustrine

(rb) (u) (p) littoral (lt) limnetic (lm) (fp)

sites: ash-layer (a), freeze box (f) n 20 a 40 a 9 a 5 a 3 f 77

min PbAA to max PbAA ppm Pb 1800 to 5400 1400 to 6600 1100 to 7500 1300 to 3500 2800 to 5200 1100 to 7500

mode of PbAA ppm Pb 1800

arith mean + stdev of PbAA ppm Pb 3400 + 990 3600 + 1600 2800 + 2100 2300 + 900 4100 + 1200 3400 + 1500

coefficient of variation 0.29 0.44 0.75 0.39 0.29 0.44

peakedness -0.26 -1.39 2.16 -1.24 -0.63

peakedness (ln of data) -1.03

skewness 0.27 0.21 1.53 0.51 -0.94 0.46

skewness (ln of data) -0.22

geometric mean of PbAA ppm Pb 3200 3200 2300 2100 4000 3000

median of PbAA ppm Pb 3300 3800 1900 2100 4400 3300

fp area of Pb-rich sedimentsakm2 2.2 14.0 19.6 8.3 9.6 53.7

(ds km2) / ( fp km2) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(ads / afp)(median ppm Pb) 132 + 988 + 684 + 315 + 792 = 2911

 area-wtd average of medians ppm Pb 2900

relative difference in means df

PbAA(u) > PbAA(lt) 8

PbAA(rb) > PbAA(lt) 7

PbAA(lt) < PbAA(lm) 3

PbAA(p) < PbAA(lm) 6

PbAA(u) > PbAA(p) 9

PbAA(rb) < PbAA(lm) 2

PbAA(rb) > PbAA(p) 8

PbAA(p) > PbAA(lt) 10

PbAA(u) < PbAA(lm) 3

PbAA(rb) < PbAA(u) 56

Entire 

floodplain

0.51

54% (possibly different)

49% (possibly not different)

51% (possibly different)

0.46

0.10

0.34 66% (possibly different)

76% (probably different)

0.42

0.49

58% (possibly different)

P(T<=t) two-tail probability of difference in populationsb

0.03

0.04

97% (significantly different)

96% (significantly different)

0.59 41% (possibly not different)

90% (probably different)

b. Probability that these two compared data sets represent populations that are statistically different.

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

Levee (lv)

Lacustrine

Depositional setting (ds)

Flood basin (fb) Summary statistics for 

thickness-weighted average ppm Pb 

in sediments of the AA (after-ash) 

time-stratigraphic interval 

(PbAA)

Units

Sedimentary environment (se) 

0.24
Table 5. Baseline Depositional Rates and Lead Concentrations,a

 and Lead in Surface-Sedimentsb of Selected Wetlands

sites sites mean std dev CV

n cm/10y ppm Pb n ppm Pb ppm Pb y

Floodplain Palustrine mean + stdev 24 to 125 y at + 1 stdev 18 2.5 + 1.7 2800 + 2100 20 to 40

Floodplain Littoral mean + stdev 26 to 100 y at + 1 stdev 7 2.4 + 1.4 2300 + 900 21 to 42

Lane Marsh South

Palustrine Near opening in barrier 1 3.9 4100 6 1600 +/- 1500 0.94 13 to 26

Lane Marsh North Palustrine 0 no data no data 6 4900 +/- 1700 0.35 no data

Levee backslope 3 11 to 21 5100 to 5700 9 4300 +/- 1500 0.35 5 to 9

Medicine Lake

Palustrine, Littoral Lateral margins of lake 2 0.5 to 2.9 1300 to 1600 7 2200 +/- 1200 0.55 17 to 200

Distributary levee Distributary-littoral transition 3.4 2100 15 to 29

Limnetic Lake bottom 1 Pb, 2 sdr 3.6 to 4.3 5200 12 to 28

Medicine Marsh

Palustrine Behind 2 barriers 1 1.0 170 11 3400 +/- 5700 1.68 50 to 100

Levee backslope Between river and barrier 0 no data no data 5 5700 +/- 5100 0.89 no data

Cave Lake

Littoral 0 no data no data 8 440 +/- 560 1.27 no data

Limnetic 0 no data no data 6 3100 +/- 2800 0.90 no data

Levee backslope 0 no data no data 5 850 +/- 460 0.54 no data

Bare Marsh

Palustrine 26 1500 +/- 1600 1.07

Levee backslope 4 4300 +/- 1900 0.44

Thompson Lake

Palustrine, Littoral Distal floodplain margin 1 2.5 290 20 4000 +/- 3200 0.80 20 to 40

Limnetic 1 2.7 2800 4 3200 +/- 630 0.20 19 to 37

Levee backslope 0 no data no data 3 3800 +/- 2600 0.68 no data

Thompson Marsh

Palustrine 0 no data no data 19 1400 +/- 1600 1.14 no data

Levee backslope 0 no data no data 3 6600 +/- 4900 0.74 no data

Anderson Lake

Littoral South of straight river reach 0 no data no data 6 600 +/- 980 1.63 no data

Distributary levee Transitional to littoral 1 3.9 3500 13 to 25

b. Surface sample intervals were 0 to 5 cm (Fousek, 1996), or 0 to 10 cm (Campbell and others, 1999), the sedimentary surface below superficial duff being recorded as the 0 depth.

c. Bold type indicates data for areas under consideration for cleanup. Data for relevant nearby areas are in italics.

d. Depositional settings classified by comparing sample locations with surficial geology mapped by Bookstrom and others (1999).

e. Barriers include the railroad embankment, road embankments, and dikes at various distances from the river.

Area identified for 

cleanup 

and surroundings

Years to 

deposit 

5 to 10 cm 

a. Baseline sample interval was from the sedimentary surface (and below surficial duff) to top of 1980 Mt. St. Helens volcanic-ash interval (or to 1/2 the thickness of the non-layered, 

homogeneous, water-saturated, organic-rich sediments above laminated sediments in limnetic sections of Pb-rich sediments).

+/-

Depositional settingd

16 to 32

Between river and barrier e

Setting comments

Baseline interval 

North of straight river reach

Pb concentrations in surface sediments 

(0 to 5 or 10 cm depth)

Behind barrier and distal from 

Medicine Lake distributary

1 3.1

Near outer side of meander

1200 Levee-marsh transition, near 

margin of meander

Sediment-deposition rates (sdr) 

and Pb concentrations 
Table 6. Sediment-Deposition Rates, Medicine-Lake Site M92CS

(after Rember and others, 1993 and Hoffmann, 1995)

Depth

Medicine Lakebottom sediments, 

site M92CS.

Time-stratigraphic 

intervals, 

Cs isotopic episodes

(cm) top of drill core (dates)a

 Tailings-release interval 

137Cs decay 

(1964 - 1969)

36 bottom of drill core bottom in BA2 interval nd nd nd nd nd nd

a.Cs isotopic dating by Rember and others (1993) indicates depths to 1951, 1964 and 1969 time-stratigraphic levels. 

Depth to 1980 time-stratigraphic level is approximated, assuming AA and BA1 sedimentation rates were about the 

same (after disposal of tailings into streams ended in 1968-69.

sdr 

PBR 

partial 

interval 

7.8

Sediment-deposition rate (sdr)

(cm/10y)

Depth span Time span

water-saturated, 

organic-rich 

sediments

4.3

Tailings-release interval 

137Cs accumulation, 

(1951 - 1964)

sdrAA 

~4.3

sdrBA1 

~4.3

18

32

alternating lightand dark-colored 

layers of sediments 

of partial BA2 

interval

16.0

10.8

sdr BA2 

partial 

interval 

12.2

8

10

10 2.3

~5.2

~4.8

Baseline interval 

(1980 - 1992)

Post-tailings-release 

interval (~1969-1980)

(cm)

1.1

sdrAA 

~4.3

sdr BA 

partial 

interval 

9.2

(y/10)

0.5

14 1.3

1.2
Table 7. Lead in Lateral-Lake-Bottom Sediments of Baseline (AA), 

Post-Tailings-Release (BA1) and Historic (BA) Intervals

depth 

interval sediment type

sedimentdeposition 

rate

Pb mean ccn 

+ stdev

(cm) description (cm/10y) (ppm Pb)

silt, 68 wt pct

0 to 4 sand, 21 wt pct 3.6 5200 + 1200

clay, 11 wt pct

silt, 68 wt pct

4 to 8 sand, 21 wt pct 3.6 5900 + 1200

clay, 11 wt pct

silt, 86 wt pct

4 to 52 + clay, 9 wt pct > 6.2 5000 + 2000

sand, 6 wt pct

(cm) description (cm/10y) (ppm Pb)

0 to 5 4.5 4400 + 170

5 to 10 4.5 4100 + 150

5 to 50 5.8 12000 + 9600

(cm) description (cm/10y) (ppm Pb)

0 to 3 2.7 2800 + 85

3 to 6 2.7 2800 + 92

6 to 48 + >= 5.5 7800 + 4500

homogeneous, 

non-layered

inhomogeneous, 

layered, silty1

non- layered

Historic BA interval 

(~1903 to 1980)

Time-stratigraphic 

interval or sub-interval

Historic BA interval 

(~1903 to 1980)

inhomogeneous, 

layered

Baseline AA interval 

(1980 - 1991)

Historic BA interval 

(~1903 to 1980)

1. Bender (1991) reported "metallic silt" in nearby piston core KB.

Post-tailings-release 

BA1 sub-interval 

(~1969 to 1980)

Baseline AA interval 

(1980 - 1991)

Medicine-Lake distributary inlet delta

M91A freeze-box sample site (Hoffmann, 1995)

T91A freeze-box sample site (Hoffmann, 1995)

Time-stratigraphic 

interval or sub-interval

91SBKF2 freeze-box sample site (Bender, 1991)

Killarney Lake, deepest middle part

homogeneous, 

non-layered

Post-tailings-release 

BA1 sub-interval 

(~1969 to 1980)

Time-stratigraphic 

interval or sub-interval

Post-tailings-release 

BA1 sub-interval 

(~1969 to 1980)

Thompson Lake, deepest eastern part

non- layered Baseline AA interval 

(1980 - 1991)
Table 8. Sediment-Deposition Rates for Paired Baseline and Historic Intervals

 (sdrAA and sdrBA)

Riverbank Upland Palustrine

(rb) (u) (p) Littoral 

(lt)

Limnetic 

(lm) (fp)

AA depositional rate (sdrAA)

sites: ash-layer (a), freeze box (f) n 22 a 14 a 6 a 1 a 3 f 46

min sdrAA to max sdrAA cm/10y 1.9 - 28.6 1.1 - 13.8 2.1 - 3.6 2.7 - 4.5 1.1 - 28.6

mode sdrAA cm/10y 3.8 1.7 3.1

arithmetic mean + stdev sdrAA cm/10y 8.5 + 6.1 3.6 + 3.6 2.8 + 0.5 3.3 3.6 + 0.9 5.8 + 5.3

coefficient of variation 0.72 1.00 0.18 0.25 0.91

peakedness 4.71 4.96 -0.77 6.83

skewness 1.87 2.28 0.13 0 2.28

geometric mean of sdrAA cm/10y 6.9 2.7 3.6 4.3

median of sdrAA cm/10y 7.3 2.3 2.9 3.3 3.6 3.6

nlt fp area of Pb-rich sediments km2 2.2 14.0 19.6 8.3 9.6 53.7

(depo setting area) / (nlt fp area)b

(ads/afp) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(ads/anl fp)(med sdrAA) 0.29 + 0.60 + 1.04 + 0.50 + 0.76 = 3.19

area-wtd median of sdrAA cm/10y 3.2

BA sedimentation rate (sdrBA) (rb) (u) (p) (lt) (lm) (nlt fp)

sites: ash-layer (a), freeze box (f) n 22 a 14 a 6 a 1 a 3 f 46

min sdrBA to max sdrBA cm/10y 0.9 - 35 1.0 - 20 0.0 - 14 5.4 - 6.2 0 - 35

mode sdrBA cm/10y 3.4

arithmetic mean + stdev sdrBA cm/10y 10 + 8.4 6.1 + 5.5 4.9 + 4.7 3.2 5.8 + 0.4 7.8 + 7.3

coefficient of variation 0.84 0.9 0.96 0.07 0.94

peakedness 2.6 1.7 3.0 3.5

skewness 1.3 1.5 1.5 1.6

geometric mean of sdrBA cm/10y 6.8 4.3 5.8 5.2

median of sdrBA cm/10y 10 3.6 4.0 3.2 5.8 4.7

nlt fp area of Pb-rich sediments km2 2.2 14.0 19.6 8.3 9.6 53.7

(depo setting area) / (nlm fp area) (ads/anl fp) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(ads/anl fp)(med sdrBA) 0.40 + 0.94 + 1.44 + 0.48 + 1.04 = 4.30

area-wtd average of medians cm/10y 4.3

relative difference in means df

sdrBA (rb > lm) 22

sdrBA (rb > p) 15

sdrBA (rb > u) 34

sdrBA (u > p) 11

sdrBA (p < lm) 5

sdrBA (u > lm) 14

sdrAA(lm) < sdrBA(lm) 3

sdrAA(fp) < sdrBA(fp) 83

sdrAA(u) < sdrBA(u) 22

sdrAA(p) < sdrBA(p) 5

sdrAA(rb) < sdrBA(rb) 38

Entire 

floodplain

b. Probability that these two compared data sets represent populations that are statistically different.

0.16

0.44

0.33

84% (probably different)

67% (possibly different)

56% (possibly different)

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

P(T>=t) two-tail

0.02

0.06

Depositional setting (ds)

Lacustrine

Summary statistics, 

sediment-deposition rates for 

Pb-rich floodplain sediments, 

deposited after (AA) and 

before (BA) the 1980 volcanic ash*

Unit

0.60

0.09

0.65 35% (possibly not different)

91% (probably different)

40% (possibly not different)

94% (probably different)

probability of difference in populationsb

98% (significantly different)

0.03

0.13

97% (significantly different)

87% (probably different)

0.81 19% (probably not different)
Table 9. Sediment-Deposition-Rate Ratios for Paired Baseline and Historic Intervals (sdrAA/sdrBA)*

 in Non-Littoral Floodplain Settings

Riverbank Upland Palustrine Limnetic

(rb) (u) (p) (lm) (nlt fp)

sites: ash-layer (a), freeze-box (f) n 22 a 14 a 7 a 3 f 43

min ratio to max ratio sdrAA/sdrBA 0.1 to 10.3 0.1 to 1.9 0.2 to 1.0 0.50 to 0.78 0.1 - 10.3

mean + stdev of ratios sdrAA/sdrBA 1.72 + 2.33 0.76 + 0.46 0.65 + 0.37 0.62 + 0.14 1.24 + 1.75

coefficient of variation 1.35 0.61 0.48 0.23 1.41

geometric mean of ratios sdrAA/sdrBA 1.01 0.62 0.54 0.61 0.81

median of ratios sdrAA/sdrBA 1.05 0.79 0.73 0.58 0.84

nlt fp area of Pb-rich sedimentsakm2 2.2 14.0 19.6 9.6 45.4

(depo-setting area) / (nl fp area) ads / anl fp x 0.05 x 0.31 x 0.43 x 0.21

(ads/anl fp)(med sdrAA/srBA) 0.05 + 0.24 + 0.32 + 0.12 = 0.73

area-wtd average of medians sdrAA/sdrBA 0.73

relative difference in means P(T>=t) 2-tail df

sdrAA/BA (rb > lm) 0.04 22

sdrAA/BA (rb > p) 0.05 24

sdrAA/BA (rb > u) 0.07 24

sdrAA/BA (u > lm) 0.35 12

sdrAA/BA (u > p) 0.56 15

sdrAA/BA (p > lm) 0.85 8

(rb) (u) (p) (lm) (nl fp)

10 9 4 3 26

1 2 3 0 6

11 3 0 0 14

* sdrAA/sdrBA ratios are for sites where both AA and BA sediment-deposition rates were calculated from measurements of full or 

nearly full sections of Pb-rich sediments, divisible into AA and BA time-stratigraphic intervals.

non-littoral 

floodplain 

Depositional setting (ds)

Summary statistics for AA/BA 

sediment-deposition-rate ratios 

sdrAA/sdrBA ratios

Units

sdrAA/sdrBA < 0.95

probability of difference in populationsb

96% (significantly different)

95% (significantly different)

sdrAA/sdrBA = 0.95 to 1.05

93% (probably different)

65% (possibly different)

44% (possibly not different)

15% (probably not different)

b. Probability that these two compared data sets represent populations that are statistically different.

sdrAA/sdrBA > 1.05

Number of sites where:

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.
Table 10. Lead Concentrations in Sediments of Paired Baseline and Historic Intervals

(PbAA and PbBA) 

Riverbank Upland Palustrine Littoral Limnetic

PbAA (rb) (u) (p) (lt) (lm) (fp)

sites: ash-layer (a), freeze-box (f) n 7 a 13 a 4 a 1 a 3 f 28

min PbAA to max PbAA ppm Pb 1800 - 4600 1400 - 6100 1100 - 7500 2800 to 5200 1100 - 7500

arithmetic mean + stdev of PbAA ppm Pb 3500 + 900 3200 + 1600 2800 + 3100 2100 4100 + 1200 3100 + 1700

coefficient of variation 0.25 0.50 1.11 0.29 0.55

peakedness 1.07 -1.28 3.94 0.09

skewness -0.81 0.52 1.98 -.94 0.79

geometric mean of PbAA ppm Pb 3300 2800 2000 4000 2700

median of PbAA ppm Pb 3300 2700 1300 2100 4400 3100

area of Pb-rich sedimets km2 2.2 14.0 19.6 8.3 9.6 57.3

(depo setting area) / (floodplain area)a

(ads/afp) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(ads/afp)(med ppm Pb) 132 + 702 + 468 +315 + 792 = 2409

area-wtd average of medians 2400

PbBA Units (rb) (u) (p) (lt) (lm) (fp)

sites: ash-layer (a), freeze-box (f) n 7 a 13 a 5 a 3 f 28

min PbBA to max PbBA ppm Pb 1500 - 8500 1200 - 11,000 780 - 14,000 5000 to 12,000 780 - 14,000

arithmetic mean + stdev of PbBA ppm Pb 4600 + 2100 5900 + 2800 6800 + 5500 2900 8300 + 3500 5900 + 3200

coefficient of variation 0.46 0.47 0.81 0.42 0.54

peakedness 2.34 -0.26 1.2 0.42

skewness 0.61 -0.06 0.56 0.59 0.63

geometric mean of PbBA ppm Pb 4200 5100 4500 7800 4900

median of PbBA ppm Pb 4600 5700 6300 2900 7800 5400

(depo setting area) / (fldpln area)a

(ads/afp) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(ads/afp)(median ppm Pb) 184 + 1482 + 2268 + 435 + 1404 = 5773

area-wtd average of medians ppm Pb 5800

differences: med PbAA - med PbBA ppm Pb -1300 -3000 -5000 -800 -3400 -2300

ppm Pb -3000

ratios: med PbAA / med PbBA 0.71 0.47 0.2 0.72 0.56 0.57

0.41

P(T<=t) 2-tail) df

0.19 3

0.26 16

0.36 3

0.48 4

0.69 4

0.77 4

0.0004 41

0.006 19

0.19 2

0.21 8

0.25 5

b. Probability that these two compared data sets represent populations that are statistically different.

probability of difference in populationsb

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

area-wtd av, PbAA medians - area-wtd av, PbBA medians

area-wtd av, PbAA medians / area-wtd av, PbBA medians

81% (probably different)

74% (possibly different)

64% (possibly different)

52% (possibly different)

31% (possibly not different)

100% (significantly different)

81% (probably different)

PbAA(u) < PbBA(u)

PbAA(lm) < PbBA(lm)

PbBA (rb < p) 

PbBA (p < lm) 

PbBA (u < p)

99% (significantly different)

Lead-concentration summary statitstics 

for pairs of AA and BA intervals 

(PbAA and PbBA)

Units Entire 

floodplain 

Depositional setting (ds)

relative difference in means

PbBA (rb < lm) 

79% (probably different) 

75% (probably different)

PbAA(rb) < PbBA(rb)

PbAA(p) < PbBA(p)

PbBA (rb < u)

PbBA (u < lm) 

PbAA(fp) < PbBA(fp)

23% (probably not different)
Table 11. Lead-Concentration Ratios of Paired Baseline and Historic Intervals 

(PbAA / PbBA)

Riverbank Upland Palustrine Littoral Limnetic

(rb) (u) (p) (lt) (lm) (fp)

sites: ash-layer (a), freeze-box (f) n 7 a 13 a 4 a 1 a 3 f 28

min ratio to max ratio PbAA/PbBA 0.39 - 1.20 0.16 - 1.50 0.16 - 1.42 0.36 - 1.04 0.16 - 1.50

arithmetic mean + stdev of ratios PbAA/PbBA 0.84 + 0.26 0.66 + 0.39 0.60 + 0.57 1.19 0.59 + 0.39 0.71 + 0.38

coefficient of variation (CV) 0.31 0.59 0.95 0.66 0.54

peakedness 0.57 0.08 2.43 -0.82

skewness -0.54 0.53 1.58 1.73 0.27

median of ratios PbAA/PbBA 0.88 0.64 0.41 1.19 0.37 0.72

(depo setting area) / (floodplain area)a

(ads/afp) x 0.04 x 0.26 x 0.36 x 0.15 x 0.18 x 0.99

(ads/afp)(median of ratios) 0.04 + 0.17 + 0.15 + 0.18 + 0.07 = 0.61

area-wtd average of medians PbAA/PbBA 0.61

relative difference in means df

PbAA/PbBA (rb > u) 17

PbAA/PbBA (rb > lm) 3

PbAA/PbBA (rb > p) 4

PbAA/PbBA (u > lm) 3

PbAA/PbBA (u > p) 4

PbAA/PbBA(p > lm) 5

(rb) (u) (p) (lt) (lm) (fp)

5 10 3 0 2 20

1 2 0 0 1 4

1 1 2 1 0 5

b. Probability that these two compared data sets represent populations that are statistically different.

PbAA/PbBA = 0.95 to 1.05

PbAA/PbBA > 1.05

P(T>=t) two-tail

0.24

0.38

Number of sites where:

21% (probably not different)

62% (possibly different)

Depositional setting (ds)

Flood basin

76% (probably different)

probability of difference in populationsb

Entire 

floodplain 

Levee

Units Summary statistics for 

PbAA/PbBA ratios

0.79

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

0.47

0.84

0.98

53% (possibly different)

16% (probably not different)

2% (practically not different)

PbAA/PbBA < 0.95
Table 12. Lead Concentrations of Sediments in Paired Baseline- and

Early Post-Tailings-Release Intervals (PbAA and PbBA1)

Riverbank Upland Palustrine Limnetic

AA-interval ppm Pb (PbAA) (rb) (u) (p) (lm) (nlt fp)

sites: ash-layer (a), freeze-box (f) n 3 a 5 a 2 a 3 f 13

min PbAA - max PbAA ppm Pb 3300 - 4200 1700 -5700 1200 - 2600 2800 - 5200 1200 - 5700

arithmetic mean + stdev of PbAA ppm Pb 3700 + 450 3300 + 2000 1900 + 1000 4100 + 1200 3400 + 1500

coefficient of variation 0.12 0.61 0.53 0.29 0.44

peakedness -3.14 -1.33

skewness 0.99 0.63 -0.94 0.14

geometric mean of PbAA ppm Pb 3700 2800 1800 4000 3000

median of PbAA ppm Pb 3600 2000 1900 4400 3300

area of Pb-rich sediments km2 2.2 14.0 19.6 9.6 45.4

(depo setting area) / (nlt fp area)a (ads/anlt fp) x 0.05 x 0.31 x 0.43 x 0.21 x 1.00

(ads/anlt fp)(median ppm Pb) 180 + 620 + 817 + 924 = 2541

area-wtd average of medians of PbAA ppm Pb 2500

BA1-interval ppm Pb (PbBA1) (rb) (u) (p) (lm) (nlt fp)

sites: ash-layer (a), freeze-box (f) n 3 a 5 a 2 a 3 f 13

min of Pb BA1 - max of PbBA1 ppm Pb 2800 - 4000 1900 - 6700 2600 - 2800 2800 - 5900 1900 - 6700

arithmetic mean + stdev of PbBA1 ppm Pb 3300 + 640 4700 + 1800 2700 + 130 4300 + 1600 4000 + 1500

coefficient of variation 0.19 0.38 0.05 0.37 0.38

peakedness 1.16 -0.77

skewness 1.58 -0.87 0.48 0.53

geometric mean of PbBA1 ppm Pb 3200 4300 2700 4100 3700

median of PbBA1 ppm Pb 3000 5200 2700 4100 4000

(depo setting area) / (nlt fp area)a (ads/anlt fp) x 0.05 x 0.31 x 0.43 x 0.21 x 1.00

(ads/anlt fp)(median ppm Pb) 150 + 1612 + 1161 + 861 = 3784

area-wtd average of medians of PbBA1 ppm Pb 3800

Comparisons of PbAA vs PbBA1: (rb) (u) (p) (l) (nlt fp)

Difference: medPbAA - medPbBA1 ppm Pb + 600 - 3200 - 800 + 300

- 1300 

1.20 0.38 0.70 1.07

0.66

relative difference in means df

PbAA(u) > PbBA1(u) 8

PbAA(nlt fp) < PbBA1(nlt fp) 24

PbAA(rb) < PbBA1(rb) 4

PbAA(p) < PbBA1(p) 1

PbAA(lm) < PbBA1(lm) 4

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

0.31

0.39

0.46

69% (possibly different)

61% (possibly different)

54% (possibly different)

0.91 9% (probably not different)

Non-littoral 

floodplain Units Lead-concentration summary statistics for AA and BA1 intervals

Depositional setting (ds)

b. Probability that these two compared data sets represent populations that are statistically different.

0.27 83% (probably different)

P(T<=t) two-tail probability of difference in populationsb

area-wtd av of ds medians of PbAA - area-wtd av of ds medians of PbBA1

area-wtd av of medians of PbAA / area-wtd av of medians of PbBA1

Ratio: med PbAA / medPbBA1
Table 13. Lead-Concentration Ratios of Paired Baseline- and Early Post-Tailings-Release Intervals

 (PbAA / PbBA1)

Riverbank Upland Palustrine Lacustrine 

limnetic

(rb) (u) (p) (lm) (nlt fp)

sites with 1980 ash layer n 3 5 2 3 13

min ratio to max ratio PbAA/PbBA1 1.05 - 1.20 0.33 - 1.01 0.45 - 0.93 0.88 - 1.20 0.33 - 1.20

arithmetic mean + stdev of ratios PbAA/PbBA1 1.14 + 0.08 0.71 + 0.29 0.69 + 0.34 0.98 + 0.10 0.87 + 0.28

coeffient of variation 0.07 0.41 0.49 0.1 0.32

peakedness -2.30 -0.27

skewness -1.55 -0.53 -0.93

geometric mean of ratios PbAA/PbBA1 1.14 0.65 0.65 0.98 0.81

median of ratios PbAA/PbBA1 1.18 0.84 0.69 1.00 0.93

(depo setting area) / (floodplain area)a

(ads/anl fp) x 0.05 x 0.31 x 0.43 x 0.21 x 1.00

(ads/anl fp)(median ppm Pb) 0.06 + 0.26 + 0.30 + 0.21 = 0.83

area-wtd average of medians PbAA/PbBA1 0.83

relative difference in means P(T<=t) 2tail df

PbAA/BA1(rb > u) 0.03 5

PbAA/BA1 (rb > lm) 0.09 4

PbAA/BA1 (u < lm) 0.11 5

PbAA/BA1 (rb > p) 0.31 1

PbAA/BA1 (p < lm) 0.44 1

PbAA/BA1 (u > p) 0.95 2

(rb) (u) (p) (lm) (nlt fp)

0 4 2 1 7

0 1 0 1 2

3 0 0 1 4

91% (probably different)

89% (probably different)

b. Probability that these two compared data sets represent populations that are statistically different.

PbAA/PbBA1 = 0.95 to 1.05

Number of sites where:

probability of difference in populationsb

69% (probably different)

56% (probably different)

5% (practically not different)

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

Units Summary statistics for 

PbAA / PbBA1 ratios

PbAA/PbBA1 > 1.05

97% (significantly different)

Depositional setting (ds) Non-littoral 

floodplain

PbAA/PbBA1 < 0.95
Table 14. Estimated Amounts of Lead-Rich Sediments, and Tonnages of Lead Deposited per Decade during 

 Baseline (AA), Historic (BA), and Background (BG) Intervals, Coeur d'Alene River Floodplain

Littoral Limnetic

cm/10y (rb) (u) (p) (lt) (lm) (fp) Source

cm/10y 7.3 2.3 2.9 3.3 3.6 3.2 table 8

cm/10y 10.0 3.6 4.0 3.2 5.8 4.3 table 8

cm/10y 2.00 0.95 0.95 0.95 0.95 0.99 text

Mm s

3

/10y (rb) (u) (p) (lt) (lm) (fp) Source

km 2 2.2 14.0 19.6 8.3 9.6 53.7 Bookstrom a

Mms

3

/10y 0.16 0.32 0.57 0.27 0.35 1.72 calculated

Mms

3

/10y 0.22 0.50 0.78 0.27 0.56 2.20 calculated

Mms

3

/10y 0.04 0.13 0.19 0.08 0.09 0.53 calculated

Mt s/10y (rb) (u) (p) (lt) (lm) (fp) Source

t s/m s

3

1.51 1.34 1.00 1.13 1.07 1.13 Bookstrom b

0.04 0.26 0.36 0.15 0.18 0.99 calculated

0.06 0.35 0.36 0.17 0.19 1.13 calculated

Mts/10y 0.24 0.43 0.57 0.31 0.37 1.94 calculated

Mts/10y 0.33 0.68 0.78 0.30 0.60 2.49 calculated

Mts/10y 0.07 0.18 0.19 0.09 0.10 0.60 calculated

ppm Pb (rb) (u) (p) (lt) (lm) (fp) Source

tPb/Mts 3300 2700 1300 2100 4400 2400 table 10

tPb/Mts 4600 5700 6300 2900 7800 5800 table 10

tPb/Mts 26 26 26 26 26 26 text

t Pb /10y (rb) (u) (p) (lt) (lm) (fp) Source

tPb/10y 800 1200 740 650 1600 5000 calculated

tPb/10y 1500 3900 4900 870 4600 16,000 calculated

tPb tirPbBG (before 1886) /10y 1.7 4.6 4.8 2.3 2.5 16 calculated

a. Bookstrom and others (2001) estimated areas of floodplain depositional settings covered by Pb-rich sediments.

Median of sediment-deposition rate (sdr)

sdr = decadal average increase in thickness

(tir Pb ) = (Mt s/10y)(t Pb /Mt s)

tirPbAA (1980 ~1993)

tirPbBA (~1903-1980)

Lead tonnage-increase rate (tirPb)

ppm PbAA (1980 ~1993)

ppm PbBA (~1903-1980)

ppm PbBG (before 1886)

median of thickness-wtd average ppm Pb

stirAA (1980 ~1993)

stirBA (~1903-1980)

stirBG (before 1886)

svirAA (1980 ~1993)

svirBA (~1903-1980)

svirBG (before 1886)

Median of ppm Pb in sediments 

Sediment tonnage-increase rate (stir)

Median of density of dry Pb-rich seds

proportion of area of Pb-rich sediments

area-wtd average of dry sed density

stir = (t s/m 3)(Mm s

3

/10y)

Sediment volume-increase rate (svir) 

Fldpln. 

(areawtd)

sdrAA (1980 ~1993)

sdrBA (~1903-1980)

River- Source

bank

b. Bookstrom and others (2001) calculated densities of dry floodplain sediments in different depositional settings, on the basis of data 

from Balistrieri and others (2000) and USEPA (1998).

Upland Palust. Lacustrine Lead-deposition rate factor by time-stratigraphic interval Units

Depositional setting

sdrBG (before 1886)

Area of Pb-rich sediments

svir = (km 2)(0.01*cm/10y)
Table 15. Estimated Tonnage of Lead in Lead-Rich Sediments 

on the Floor of the Coeur d'Alene River Valley in about 1993 

Pb-tonnage factor 

by time interval units Floodplain Riverbed Dredge spoils Valley floor

Baseline (AA) interval (1980~1993) (fp) (rb) (ds) (vf)

number of sites n 48 0 0 48

Lead deposition rate (kt Pb/10y) 5.0

Depositional time interval *(10 y) *(1.3)

Pb tonnage deposited kt Pb 6.5

Historic (BA) interval (~1903-1980) (fp) (rb) (ds) (vf)

number of sites n 48 0 0 48

Pb deposition rate kt Pb/10y 16

Depositional time interval *(10 y) *(7.7)

Pb tonnage deposited kt Pb 123

Total for Historic and Baseline 

intervals (~1903~1993) (fp) (rb) (ds) (vf)

number of sites n 48 0 0 48

kt of Pb + 30% kt Pb 123 + 37a

(Bookstrom and others, 2001) (fp) (rb) (ds) (vf)

number of sites for thickness of 

section of Pb-rich sediments nThk 297 336 20 653

number of sites for thickness-wtd 

average ppm Pb nPb 130 31 10 171

median-based estimates + 30% kt Pb 79 + 24 129 + 39 44 + 13 252 + 76

mean-based estimates + 30% kt Pb 131 + 39 120 + 36 69 + 21 320 + 96

(fp) (rb) (ds) (vf)

number of sites for wtd av ppm Pb nPb 48 31 10 89

rounded median-based estimatesb

kt Pb 120 + 40 290 + 90

source this report total

b. These estimates are rounded to two significant figures.

Previous estimates of tonnage of lead in lead-rich sediments on CdA River-valley floora

a.This median-based estimate for the tonnage of lead in lead-rich floodplain sediments (117 + 36 kt of Pb) 

is based on a sub-set of the data included in previous estimations of median- and mean-based estimates by 

Bookstrom and others (2001). Only full or nearly full sections of lead-rich sediments, in which the AA and 

BA intervals could be identified, were used in this study. The sum of relative analytical uncertainties was 

approximated as + 30 percent by Bookstrom and others (2001).

170 + 50

Bookstrom and others 

(2001)

Combined estimate of tonnage of lead in lead-rich floodplain sediments 
Table 16. Estimated Tonnage of Lead-Rich Sediment Released Annually by Riverbank Erosion, 

Coeur d'Alene River, West of Cataldo Landing

Total area 

of eroding 

bank face

Total 

tonnage of 

eroded 

sediment

m

2 kt/y

median-based estimates

length of reach (m) 14,600 10,300 17,500 17,700

length of banks (m) 29,200 20,600 35,000 35,400

med height of Pb-rich bank (m) 0.99 0.79 0.58 0.38

area of bank face (m2) 28,908 16,274 20,300 13,452 78,943

med width (m/y of bank eroded) 0.051 0.051 0.051 0.051

volume (m3/y of bank eroded) 1,474 830 1,035 686

density of sediment (t/m3) 1.51 1.51 1.51 1.51

t/y of bank sediment eroded 2,226 1,253 1,563 1,036 6.079

6.1

mean-based estimates

length of reach (m) 14,600 10,300 17,500 17,700

length of banks (m) 29,200 20,600 35,000 35,400

mean height of Pb-rich bank (m) 1.03 0.85 0.63 0.49

area of bank face (m2) 30,076 17,510 22,050 17,346 86,982

mean width (m/y of bank eroded) 0.089 0.089 0.089 0.089

volume (m3/y of bank eroded) 2,677 1,558 1,962 1,544

density of sediment (t/m3) 1.51 1.51 1.51 1.51

t/y of bank sediment eroded 4,042 2,353 2,963 2,331 11.689

11.7

* RBW 0-1 indicates riverbank-wedge deposits of lead-rich sediments along river segments 0 to 1. Locations of 

numbered river-segments are shown on maps in figures 3, 4, and 5. 

Total of median-based estimates of bank sediments eroded (rounded)

Total of mean-based estimates of bank sediments eroded (rounded)

Riverbank reach RBW 0-1* RBW 2 RBW 3-4 RBW 5-6
Table 17. Mean Annual Sediment-Transport Rates, Coeur d'Alene River (1992-1999), and 

Baseline Sediment-Deposition Rates, Coeur d'Alene River Floodplain, and Coeur d'Alene Lake (1980 ~1983)

Riverbank 

sediment 

eroded

Riverine 

transport, 

mean 

annual rate 

+ stdev

kt sed/y kt sed/y

Bank sediment eroded (table 15, mean) 12

7 + 8

17 + 12

24 + 20

40 + 85

33 + 26

73 + 111

97 + 131

8% to 16%

Riverbank 

sediment 

eroded

Deposition, 

median of 

mean 

annual 

rates

kt sed/y kt sed/y

Bank sediment eroded (table 15, mean) 12

70

120

190

3% to 6%

50%

160

40

200

3% to 6%

390

1.5% to 3%

48%

24%

Mean annual transport, Rose Lake gage

Sediment transport, Harrison gage

Total transport, Rose Lk.+ Harrison gauges, as pct. of lead-rich sed. deposited on floodlain

Sand to silt deposited on CdA River delta toe

Total annual deposition on floodplain (median-based estimate)

Sand to silt deposited on levees and sand splays

Silt to mud deposited in marshes and lakes

Bank sediment (6-12 kt/y) as percent of sediment deposited on floodplain

Suspended sand, annual load

Suspended silt and finer, annual load

Mean annual transport, Harrison gage

Bank sed. 

eroded as 

percent of 

sediment 

transported

Sediments eroded from riverbanks, 

recorded at gauges, 

and deposited on floodplain

Bank sediment eroded (6-12 kt/y) as pct.of mean annual transport at Harrison 

Sediment transport, Rose Lake gauge

Suspended sand, annual load

Suspended silt and finer, annual load

Total transport, RL and H, as pct. of lead-rich sed. Deposited: floodplain and CdA Lake

Baseline deposition rates, floodplainb 

Baseline deposition rates, Coeur d'Alene (CdA) Lakec

Bank sed. 

eroded as 

percent of 

sediment 

deposited

Estimated annual average tonnage of sediment 

deposited on CdA River floodplain 

and in CdA Lake 

(between 1980 and 1993)

Total of lead-rich sediment deposited on floodplain and in CdA Lake

Silt to mud deposited in CdA Lake, beyond the delta toe

Annual deposition of metal-enriched sediment in CdA Lake

Total of sed transport, Rose Lake and Harrison gages

b. Decadal average tonnages of lead-rich sediment deposited on the floodplain during the baseline interval (table 13) 

were converted to kt/y. 

c. Means of baseline sediment-deposition rates for the toe of the CdA River delta and the distal lake axis (table 2) are 

converted to annual rates, which are multiplied by corresponding areas to calculate volumes of sediment deposited 

annually. The CdA River delta extends to core holes 6 and 8 of Horowitz (1995), and covers an area of about 12.5 

km2. Horowitz (1995) reported that 85 percent of the 128 km2 of the lakebed (106 km2) is covered by metal-enriched 

sediments. Of that, about 18 km2 overlaps the delta and the lower floodplain. The area of contaminated lake-bottom 

is therefore about 91 km2. To convert volume to tonnage, we multiplied by densities of 1.4 t/m3 for the delta, and 

1.07 t/m3 for distal lake-bottom sediments (from Bookstrom and others, 2001).

a. Based on 1999 measurements, Woods (2001) modeled sediment transport as a function of discharge (USEPA, 

2001). This model was applied to estimate sediment transport as a function of discharge for water years 1992 to 

1998. Summary statistics for these estimates (converted from short tons to metric kilotons) are presented above. 

Bank sed eroded as percent of lead-rich sed deposited in CdA Lake

Bank sed eroded, as pct. of lead-rich sed deposited: floodplain + CdA Lake

Total transport, Rose Lk. and Harrison, as pct. of lead-rich sed. deposited in CdA Lake

Riverine sususpended sed as percent of lead-rich sed deposited in CdA Lake

Total transport at 

RL and H gauges, 

as percent of 

Pb-rich sediment 

deposited